SVGHMI: multiple non significant changes: doc fixes, modern style access to attributes, enforce double quotes around member name in object literals.

SVGHMI: Changes /CURRENT_PAGE_* behaviour to prevent problem whith multiclient : all clients were switching page when one was jumping.
- now PLC have to prefix page name with "!" to order page switch.
- HMI do not prefix with "!" when jumping, this avoiding looping incidently
- In case of multiple client:
CURRENT_PAGE reflects current page of last client hwo did jump
Setting CURRENT_PAGE with "!" affects all clients simultaneously

SVGHMI: changes that should fix some corner cases about unlinking and discardable element that still didn't show until now.
- list that would have been declared in some groups could have been discarded.
- elements to be unlinked were comuted based on filtering $hmi_elements, whereas $hmi_widget already filtered list

SVGHMI: update generated XSLT

merged

SVGHMI: add CURRENT_PAGE_{location} global variable to reflect currently visible page. If PLC wites some valid page reference in that variable, it triggers page switch. Additionally, fixed /HEARTBEAT being subscribed systematically by JS code even when wtchdog is not enabled.

Follow-up on 83ed4ea362db 'IDE: prevent invoking matiec when IEC code did not change since last build' : build unconditionally after clean

merged

OPC-UA: fix types in model not being preserved after reload of CSV file, leading to exception when changing selection lists content.

OPC-UA: Removed more "LocalizedText()", this time in selected variable list

IDE: prevent invoking matiec when IEC code did not change since last build.

SVGHMI: prevent systematic rebuild when there are multiple instances of SVGHMI CTN.

SVGHMI: optimize HMI tree handling C code to lower CPU usage when traversing large trees

merged

SVGHMI: prevents watchdog being triggered when SVGHMI is empty.

Backed out changeset c646a1f0fb0b - was on wrong branch

Make OPC-UA client compatible with wxPython3, util wxPython4 branch deserve to be merged

Make OPC-UA client compatible with wxPython3, util wxPython4 branch deserve to be merged

IDE: Enforce wxPython3 menu appending syntax in default branch... (Fixes exception at startup)

OPCUA: fix display names appearing with a "LocalizedText(" prefix when browsing localized server.

OPCUA: Add browsing of variables exposed by client when selecting location from variable panel.

OPCUA client: fix handling of string type Node Identifier

Add OPC-UA simple synchronous client extension.

This extension uses python-opcua to growse server nodes, and generates runtime C code that use open62541.
- python-opcua must be available in python path (i.e. "import opcua" must succeed). Can be installed from pypi with "python2 -m pip install opcua --user" .
- at build time, open62541 is expected to be build in "open62541" directory, aside "beremiz" directory.

SVGHMI: update test/svghmi to reflect latest changes

SVGHMI: Update generated xslt

SVGHMI: remove "value" element in meter and circularbar widget. Adding support for printf like formating make widget label too heavy. It is better to use Display widget instead.

SVGHMI: Move sprintf.js out of widget_display.ysl2 since it is used in other widgets as well

Dropped SVGUI, deprecated and replaced by SVGHMI. Transformed traffic_lights exemple so that it uses SVGHMI instead.

SVGHMI: Update generated XSLT (PathSlider widget)

SVGHMI: simplication in ScrollBar widget JS code

SVGHMI: Added PathSlider widget

SVGHMI: update generated xslt (List related changes)

SVGHMI: add files missing in ee9e98c856a : Add TextList widget, add support for TextList in DropDown widget, move List, TextStyleList and TextList widget code in dedicated file with documentation.

SVGHMI: add test for Dropdown using TextList

SVGHMI: Add TextList widget, add support for TextList in DropDown widget, move List, TextStyleList and TextList widget code in dedicated file with documentation.

IDE: Add a "Tutorials and Examples" sub menu to "File" menu to directly open projects in /exemples directory. Move 'python' and 'first_steps' projecvts from /tests to /exemple

WxPython 3.x -> 4.x : removed exception on stdout when closing at IDE frame

Tests/svghmi_scrollbar: Fix variables names and remove useless "OnStart OnStop OnWatchdog" to use defaults.

IDE/windows: Avoid exception on quit caused by runtime being killed without disconnecting.

Runtime/unix: Fix typo preventing start of Pyro server

Fix SVGHMI exception when running on Windows, missing ENODATA in errno.

Runtime: avoids using "pipe to self" bailout unblocking trick on windows, since select() only takes sockets.

Merge deafult in wxPython4

Merge changes about wamp reconnecting options, and added missing parts so that these changes make sense.

Fixed Wamp reconnect on lost connection.

SVGHMI: force MaxConnections sum back to zero, preventing it to grow indefinitely on each build.

OPCUA: fix display names appearing with a "LocalizedText(" prefix when browsing localized server.

OPCUA: Add browsing of variables exposed by client when selecting location from variable panel.

OPCUS client: fix handling of string type Node Identifier

Add OPC-UA simple synchronous client extension.

This extension uses python-opcua to growse server nodes, and generates runtime C code that use open62541.
- python-opcua must be available in python path (i.e. "import opcua" must succeed). Can be installed from pypi with "python2 -m pip install opcua --user" .
- at build time, open62541 is expected to be build in "open62541" directory, aside "beremiz" directory.

IDE: fix wxpython4 sequel : project "add" menu was having no extension entry visible.

Prevent exception when asking for CSV dump while variable traces are still empty

Fix wrong comment

Fixed two exceptions happening when interacting with viewer(s) in debug mode, when debug data is still not initialized.

SVGHMI: update test/svghmi to reflect latest changes

SVGHMI: Update generated xslt

SVGHMI: remove "value" element in meter and circularbar widget. Adding support for printf like formating make widget label too heavy. It is better to use Display widget instead.

SVGHMI: Move sprintf.js out of widget_display.ysl2 since it is used in other widgets as well

Dropped SVGUI, deprecated and replaced by SVGHMI. Transformed traffic_lights exemple so that it uses SVGHMI instead.

Merge from default