All widgets reworked to use widget class and animate function if needed

SVGHMI: Moved JsonTable/Alarm related test in a separate page.

SVGHMI: JsonTable now ignores elements and groups starting with #

SVGHMI: Fix keypad : non-number input was always considered invalid because of missing type checking.

SVGHMI: JsonTable now updates range and position variables so that slider widget can update.

SVGHMI: Fix multiple variable support in widget

SVGHMI: Add TODOs in Button widgets.

SVGHMI: Alarm test not using Button widget anymore, too many problems. Use Input widget instead to increment value on each click and execute python code on change.

SVGHMI: little fix in HMI:Button

SVGHMI: JsonTable now use intermediate variables again to address JSON data without duplicating code or referencing. Using intermediate variables also alows to check for availability of data and stop evaluating early if data is missing. Finally added complete roundtrip example to illustrate use of JSonTable to display "alarms" collected in python from changes on PLC boolean variables.

SVGHMI: removed debug code forgotten here and there.

SVGHMI: JsonTable now makes meaningfull JSON request : all arguments and variables are passed in.

SVGHMI: Keypad is now keeping Javascript type constency. In other words, if a number was given as initial value, input value will have to convert to number in order to be valid. In case invalid value is entered, initial value is restored.

SVGHMI: Behave when project path include spaces, and make more understandable error in case of problem extracting geometry with inkscape.

SVGHMI: Refactor the way JsonTable generate javascript code to access json data. Now support multiple assignments, used in the case of text to change both content and style on the same element.

SVGHMI: Fix again clone unlinking, and this time add an "original" attribute to track the id of the original object before unlinking.

SVGHMI: Fix svg test file while testing latest JsonTableChanges

SVGHMI: HMI:JsonTable also recognize TextStyleList, but parsing of textContent is still not implemented and style is still not updated.

SVGHMI: Deeper clone unlinking. Was actually not recursive, and clones in clones where not unlinked. Stack successive ids to avoid collisions.

SVGHMI: factorize dispatch calling logic.

SVGHMI: HMI:VarInit:"a string"@a_value : empty widget (i.e. empty svg:group) that initialize content of local variables to value given as first argument.

Merge

SVGHMI: Add more local HMI variable tests in tests/svghmi.

SVGHMI: finished initial implementation of PAGE_LOCAL and HMI_LOCAL variables.

SVGHMI: add a SetPoint to Slider Widget, visible only when operating the slider.

SVGHMI: Update Slider widget so that it doesn't display future value but actual value only.

SVGHMI: provide request_animate() to Widget authors so that they can register redraw code when events lead to redraw. Widget member animate() is called when it is time to update DOM.

Merge

SVGHMI: Intermediate state while implementing local HMI variables. Now write to cache only (no send), still need to implement dispatch on change.

Beremiz test project with newly created widgets.

Rebuilded gen_index_html.xslt after all new widgets were commited

Create new multistate widget which extand class widget