SVGHMI: cosmetic fixes + removed dead code

SVGHMI: allow widgets to disable clipping on variables given with min and max. Setting this.clip = false disables clipping.

SVGHMI: allow designating widget's sub-elements as main element child rather than descendant. Names staring with "/" in yslt call to labels() only match direct widget childs.

SVGHMI: add localized Date and Time support to sprintf.js. Use with "%D" or "%2.1D" format style.

Minor changes to README.md

wxPython4 sequels: usual naming problem in grid cell change events, non kw-args to menu.Append and event not being skipped.

Tests: Fix missing <br/> in generated html report.

Tests: add HTML report generation and a workaround to bad exception handling in sikuli.

In case of exception in python code, and since a thread is running
to observe stdout, sikuli was never terminated after an exception.
Unfortunately sys.exepthook doesn't work in that version of jython/sikuli.
Test are now written inside functions witch are passed to run_test to deal
with exception.

Tests: refactored sikuli based test

IDE: Postpone execution of keyboard shortcut commands when given while previous command is still being executed, to prevent CTR/builder jamming.