SVGHMI: added "page_node" variable that reflects the HMI tree path of current relative page

SVGHMI: Add list of HMI tree path in a JS array, so that we can use it for multiple purpose :
- display name of edited variable in keypads (currently wrong in relative pages)
- have some variable that hold basename of current relative page HMI_NODE's path
- propose some list of names in DropDown when selecting a relative page to jump to, without having to instancite many jump widgets.

SVGHMI: Fixed wierd CDATA mess in output xhtml, because of backticks copy pasted in some yml ||text block||

SVGHMI: Added fonts.py with functions to convert ttf, otf and woff fonts into data_uri based CSS font-face

merge

SVGHMI: split svghmi.py into svghmi.py (Config Tree Node + code gen) and ui.py (UI for HMI tree and Widget picking)

SVGHMI: stop serving HMI open wide on all interfaces. That was a security hole. It is user/developer responsibity to forward connection with for exemple stunnel and make it securely accessible from LAN.

SVGHMI: Filter unseen geometry from inkscape CSV output.

When inkscape exports geometry form all objects, then it also includes objects from svg:defs. This makes problems when deciding if an object is part of a page, since coordinate of objects in svg:defs can eventualy be contained in a page. In the end, those objects where getting detached when leaving pages where they where found, leading for exemple to non working text on clipping when the clipped text was cloned in multiple page.

SVGHMI: Fix typo in error message formating in i18n.

SVGHMI: split svghmi.py into hmi_tree.py + svghmi.py

Merged

SVGHMI: JsonTable: Fixed options not being passed in JSON post when jumping to a page where additional variables are pre-defined by a HMI:VarInit.
Was JS Fetch Promise not executed late enough, and gathering JsonTable variables before the sequence of calls to dispatch() was finished.

SVGHMI: Added small widget library for library browser testing.

SVGHMI: Added SVG widget library browser. Supports browsing and previewing widgets. Widget validation and drag'n'drop are still to be implemented.

Allow using spin() from ProcessLogger even with no logger given.

merged