SVGHMI: Adapt svghmi.c to changes in UnpackVar

Runtime: Now retain uses a list based on data available in VARIABLES.csv instead of traversing the whole instance tree looking for RETAIN flag.

RUNTIME: Variable forcing now uses limited list and buffer instead of systematical instance tree traversal and in-tree "fvalue" to keep track of forced value for pointed variables (external, located). Pointer swapping is performed when forcing externals and located, with backup being restored when forcing is reset. Retain still uses tree traversal.

RUNTIME: Variable trace now uses limited list and buffer instead of flags in instance tree that was requiring systematical instance tree traversal, and worst size buffer. Forcing and retain still use tree traversal.

SVGHMI: more accurate filtering of elements to unlink or not

OPC-UA client: generated code now take UA_Variants on the stack directly, avoid useless allocation on write, and unalloc implicitely allocated data on read

OPC-UA client: generated code now take UA_Variants on the stack directly, avoid useless allocation on write, and unalloc implicitely allocated data on read

IDE: Tutorial/Example menu was broken : path of project being open was the same for all menu entries.

IDE: Tutorial/Example menu was broken, probably after a merge. Menu (and corresponding code) was duplicated. Also, path of project beeing open was the same for all menu entries.

Fix bug when updating data in variable panel.

Grid event naming CHANGE->CHANGING was wrong. CHANGE->CHANGED is the way to go.

SVGHMI: update tests/evghmi to reflect/test latest changes. update generated XSLT.

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