SVGHMI: Keypad: added code to re-attach keypad when starting edit.

SVGHMI: removed debug code

SVGHMI: More infrastructure for editing values with a keypad.

SVGHMI: Widget input buttons should be clickable through svg:use (onclick attribute instead of addEventListener)

SVGHMI: moved dead code to where it belongs

SVGHMI: empty widget_keypad.ysl2, WIP

SVGHMI: HMI:Switch now accepts boolean values 'true' and 'false'

SVGHMI: Jump widget, if it has a 'disabled' labeled element, reflects value of the pointed HMITree variable by showing this element when value is False, and behaving normaly otherwise.

SVGHMI: prevent man-made memory leak by limiting back button history items count to 42

SVGHMI: collect debug data through xslt reflectivity instead of yml2/python trick

SVGHMI: Jump widget can now display as active or inactive, if corresponfing "active" and "inactive labeled elements are provided.

SVGHMI: added Back widget.

SVGHMI: Jump widget now make errors if path given for relative jump doesn't match target page reference path class.

SVGHMI: Check that explicit relative page jump path is consistant with destination page reference path.