Added Getter functions to CCPACSPositionings.h

[merakulix]

Added Getter functions to CCPACSPositionings.h to make Positionings available via Python Bindings, which is currently not true for classes that store elements using the std::vector<std::unique_prt<TYPE>> and don't provide getter functions that return elements by index.

For further information see RISCSoftware/cpacs_tigl_gen#59

Description

New Functions:

CCPACSPositionings::GetPositioningCount()
CCPACSPositionings::GetPositioning(int index)

Implements Getter functions manually, as discussed in RISCSoftware/cpacs_tigl_gen#59, to fix missing functionality as described in #936.
Functions returning the type std::vector<std::unique_prt<TYPE>> will still not be available via Python Bindings.

How Has This Been Tested?

Added a test, checking missing functionality described in #936

Checklist:

Task	Finished	Reviewer Approved
At least one test for the new functionality was added.	yes does not apply	OK
New classes have been added to the Python interface.	yes does not apply	OK
The code is properly documented with doxygen docstrings	yes does not apply	OK
Changes are documented at the top of ChangeLog.md	yes does not apply	OK

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.48%. Comparing base (4adb704) to head (b5a9f3c).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1046   +/-   ##
=======================================
  Coverage   69.47%   69.48%           
=======================================
  Files         301      301           
  Lines       26887    26894    +7     
=======================================
+ Hits        18681    18688    +7     
  Misses       8206     8206           

Flag	Coverage Δ
unittests	69.48% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/CCPACSPositionings.cpp	95.71% <100.00%> (+0.47%)	⬆️

[merakulix]

I'd like to add, I formatted some docstrings that were not part of this Issue, since we discussed improving tigls generated documentation by Doxygen.