Metainfo Nexus improvements

Definitions take arbitrary json serialisable kwargs and add those to the definition (incl. its serialization). This can be used initially for any definition level properties that nexus might use. For example optional. Those would have no effect on the definition semantics yet.
Test cases for definitions that use nested Python classes
Qualified names contain the sections of parent Python classes for section definitions based on nested Python classes.
Test cases for inheritance
SubSection and Quantity definitions can be partially overwritten
Support for binary data
Adapt and test the metainfo browser for all the above.

This might become necessary in the future

support for TEMPLATE_properties (currently done via sub sections)
support for arbitrary attributes on quantities (currently done via sub sections)

Edited Dec 07, 2021 by Markus Scheidgen