Python Runtime : stil untested optimization of Python Safe Globals.

Now only one python_poll block per python extension is used to trigger
execution of OnChange calls.

Prevent global python_poll blocks to be created when accidentally adding content to C-File OnChange column.

Merge from default

Modbus: fix strange side effect of re-use of condition variables or mutex with Xenomai : without bzero of the associated types, mutex keeps locked.

Modbus: fix client timer invalid arguments.

Modbus add a timer thread, and switch timer to SIGEV_THREAD_ID to follow xenomai posix skin restrictions.

Runtime: Fix typo in PLCObject leading to exception when reporting failure.

merged

SVGHMI: Fix bug introduced when merging default

SVGHMI: Add use of Python PLC Globals it test

Merge default changes in SVGHMI

Merge default changes in SVGHMI

SVGHMI: add "unsubscribable" property to widgets in order to generalize what already happens for jump buttons.
In most cases jump buttons do not really subscribe to pointed HMI variable, path is given as a relative page jump path. When widget.unsubscribable is set to true, no subscription is made on page switch, but still offset is updated.
This fixes bug happening on relative jump buttons without "disabled" element where offset did not change on relative page switch.

merge

Merge

SVGHMI: Added widget toggleButton.

SVGHMI: Changed widget button handler to element attribute.

Runtime: create .md5 file at the end of all transfered files being written to disk, so that it presence indicates completeness of transfer.

IDE: Main toolbar : Show repair button also in stop mode. Move repair button after disconnect button.

Runtime: fsync() files when transfering them, to prebent data loss when poweroff soon after programming. Fixed variable naming as a side effect.

PLCObject : reorganize code in StartPLC(), add a PreStartPLC() empty method, to be overloaded by runtime extensions.

Solve import order problem when POULibrary imports ConfigTreeNode because of UserAddressedException. Now UserAddressedException is declared in POULibrary.py, as a quick and dirty fix, but some independant module should be created for beremiz exceptions in general.

SVGHMI: stop using eval in change_hmi_value, apparently slowly leaking memory.

SVGHMI: Switch widget was picking sub-elements from original SVG, not the result SVG ehwe clones are unlinked, thus making problems with svg:use based widgets.

SVGHMI: When unlinking a clone of a group, do not create additional group, but merge transformation and styles, and replace label. This allows svg:use based widgets to directly access elements of svg:use targeted element.

SVGHMI: Applies clone unlinking to widget themselves, not only to clones inside widgets.

merge

SVGHMI: Makes error when HMI tree is not well formed. Prevents multiple and non-first HMI_NODE, and ensure that all paths in HMI tree are unique.

Added FatalError call to Libraries code gen, so that they can emit messages addressed like config tree nodes do.

SVGHMI: more Widget properties declared ES6 style.