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

SVGHMI: cosmetic change, missing semicolon

SVGHMI: JsonTable should refresh when re-subscibing, because data might have changed while not on the page we are switching to.

SVGHMI: Fixed problems happening when value is higher than maximum or lower than minimum in Input widget. "max" and "min" string was getting into keypad text field, was not diplayed systematically, and was staying forever sometime.

SVGHMI: change default values for JsonTable, leading to scrollbar initialized at annoying non-zero position

SVGHMI: Ensure that when a HMI:List is refered, none of its refered elements are discarded.

Backed out changeset b2ba6eeb61ec. Users reported text styling being messed in some cases.

merge