IDE: Fix missing highlighted element in diagrams when using GTK3

- wx's logical function does not work on gtk3, and highlighting relies on it
- skipping logical funciion at all "works" but this now makes highlight opaque
- no easy fix for highlight transparency since emulated with AND Wx logical function
+ added other highlight related cosmetic fix.

.. Beremiz documentation master file

Beremiz's documentation
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Contents:

.. toctree::
   :maxdepth: 2

   overview
   manual/index
   standards