SVGHMI: add a class attribute to HMI Tree nodes, set when using HMI_NODE

SVGHMI: HMI_LABEL and HMI_CLASS become HMI_NODE.
- Name of parent POU becomes HMI tree node name,
- Name of HMI_NODE variable becomes class of the node.

Add FatalError() method to ConfigTreeNode.
Extensions can report error addressed to user, without a traceback.

SVGHMI: various fixes to make SVGHMI behave on more versions of twisted and GCC.

SVGHMI - prepare page with cached data when switching. This prevents values that do not change and that was already subscribed in previous page from keeping undefined.

SVGHMI: various insignificant code moves, commenting and typos fixes.

SVGHMI : fancier second page in tests/svghmi

SVGHMI: SVG viewport now defined so that HMI take scales and fit to the view. Implemented page switch through viewport change, no hiding of widget for now.

SVGHMI - added simple Meter widget.

SVGHMI: Quicker update path for input widget when pressing on buttons, do not wait until data comes back, and simply update value text of the pressed widget. Updated PLC prog for more amimated value to display

SVGHMI: fixed HMI->PLC dataflow : not updates as expected, and not initialized properly after subscribe.

Fixed one more sequel of 5f79b194fa63 'SVGHMI: filter out temporary variables created while generating ST code out of FBD.'

SVGHMI: Added relative changes of HMI value from widgets.

SVGHMI - Fixed svghmi.{c,js} about HMI -> PLC data unpack.

SVGHMI: Added init call to all widgets at startup to bind events. More features in Input widget : Edit and Change buttons. WIP HMI->PLC value update, incoherent data detected in C part on update.

SVGHMI: dispatching data to minimalist "Display" text widget.

SVGHMI: Many fixes. Subscriptions to HMItree seems to be working, and dispatch function is called in JS with good data. Bidirectional communication now really working.

SVGHMI : many details about communication implemented in JS, with side effects.

SVGHMI: added a widgets description object, accessed by id. Added frequency to widgets, as separate template to allow future customization. Excluded non svg elements (i.e inkscape Sets) with HMI: labels from widgets.

SVGHMI fix logic for page membership detection

SVGHMI compute default page

SVGHMI: deduce pages content out of geometry (elements contained in page bounding box are in)

SVGHMI: use func:function for parsing labels so that it can be used in predicates

SVGHMI: moved/fixed some templates, avoided namespace problems, added parsing of HMI:* inkscape labels

SVGHMI: now generating JS object describing widgets and pointing to SVG elements

SVGHI: compute hmitree variables ordered index in xslt

SVGHMI: now built.

SVGHMI: Work in progress. C side mostly implemented, neither built nor tested.

SVGHMI: More strict formating of active HMI labels : @ separator only used for paths

SVGHMI: new test svg to drive next implementation

Non significant changes in generated xslt, side effect of changes in yslt_noindent.yml2

Merge default in SVGHMI branch

SVGHMI: Starting to define JS side more in details.

SVGHMI: added transformation of code given in inkscape's description fields into javascript functions

SVGHMI: gui.svg -> svghmi.svg

SVGHMI: moved static JS code to a separate file included at xhtml generation time

SVGHMI: Work In Progress : fixed pointer types in ctypes interface, cleaned up server startup and cleanup code, changed document type to XHTML, cleaner JS script : encapsulated in a function and in CDATA.

PLCobject: Call "stop" and "cleanup" methods from python runtime files in reverse order compared to "init" and "start".

SVGHMI: WIP for python<->C data exchange : message from browser hit the C side.

SVGHMI: WIP for python<->C data exchange

SVGHMI: WIP for python<->C data exchange

SVGHMI: WIP for python<->C data exchange

SVGHMI: single session for now

SVGHMI: few fixes on serving

WIP on svghmi, now builds and runs. HTTP serving + WS transport ready, missing actual data to transmit and thread to collect it.

Non significant changes to mute GCC warnings about unused variables.

Fixed sequel of 5f79b194fa63 'SVGHMI: filter out temporary variables created while generating ST code out of FBD.'. Some ref to temporary variables are still not using the _TMP_ prefix. They are quite hard to find, so to be continued...

SVGHMI: Intermediate state while working on svghmi.c

svghmi.c : deduplicated variable access code borrowed from plc_debug.c. Added targets/var_access.c.

SVGHMI: Added iterators in svghmi.c copy-pasted form plc_debug.c

SVGHMI: svghmi.c now has mutex, iterator, and read/write buffer.

SVGHMI: draft for svghmi.c. It has all PLC variables pointed in HMI tree in an array.

Pass HMITree to SVG transform. It seems it could really help to reduce JS tree binding logic in the end.

Add special nodes at HMI Tree root, fix code to handle special node (no path).

Swap CTN code gen and Libraries code gen, because SVGHMI use both, and need the library part to produce hmitree before CTN part.

yslt_noindent : Avoid YSLT's indent logic to interfere when using linequote.

SVGHMI: make a reasonably basic test

SVGHMI: filter out temporary variables created while generating ST code out of FBD.

SVGHMI: added deduction of HMI tree from list of HMI_* instances.

SVGHMI: added extraction of SVG bounding boxes, obtained from "inkscape -S", and passed to XSLT transform as variable.