tests: add tesseract training data "tessdata", still trying to enhance OCR reliability in UI tests

tests: attemps to make OCR based hits more stable

Tests: fix path logic in Docker creation script, consequence of previous commit.

Tests: cleanup and tidy docker definitions and scripts

Merged changes from default in wxPython4 branch

SVGHMI: fix XY graph init (consequence of earlier change) + reindent

Earlier change did modify the variables attributes (options) are stored in widget objects. XY graph uses variables' min and max to determine range.

SVGHMI: move declaration of "xmlns" javascript const so that widgets can use it.

This was broken in earlier commit, when changing initial execution order because of implementing websocket reconnect.

SVGHMI: add Page assignment use case in svghmi test project.

Marged default in wxPython4

SVGHMI: update generated xslt

SVGHMI: avoid Widget's member name colision in between enable expressions and assignments.

SVGHMI: Add arbitrary variable assignment when entering Pages

Usage similar to Assign widget.
Required instanciating PageWidgets for each page, so that assigned variables can be subsribed.

SVGHMI: update generated XSLT

SVGHMI: fix periodic reconnect triggering watchdog

IDE: Optimization of modification events processing in text editors.

Too many modifications types where registered, and then too many events were fired.
Also, in case of uninterrupted sequence of events, updates to the model is deferred to the end of that sequence (wx.Callafter).

SVGHMI: cosmetic change