Tests: re-enable running test in github action, now that docker image should be cached.

Tests: temporary disable problematic part, to force action to succeed so caching can happen.

Tests: give test directory when creating container, not when running test.

Tests: fix docker image export for GitHub Action caching.

Tests: More fixes amd enhancments to run tests on Github Actions

Tests: use script rather than alias so that bash doesn't need to be interactive shell with a TTY

Tests: remove -it from docker invocation

Workaround "The input device is not a TTY" error on Github Action.

Create run_tests_in_docker.yml

SVGHMI: Add support for forcing widget update frequency with period longer than a second. As an example, "HMI:Display|10s@/myvar" updates variable every 10 seconds.

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.