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.