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.