Add QElmerRenderer - Githubissues

Fixes #881

Adds ElmerFEM to available renderers in qiskit-metal.

Submitting this as a draft PR. The following items need to be completed before merging:

[x] Fix name of BiCGstabl Polynomial Degree parameter to avoid duplicate.
[x] Fix net assignment issue generated when a given node is in contact with ground plane.
[x] Add/update Docstrings to all functions/methods in elmer_renderer.py.
[x] Add/update Docstrings to all functions/methods in elmer_runner.py.
[x] Add error checking within QGmshRenderer to inform user if items in open_pins list don't exist.
[x] Add warning message if no cap bodies found in design (ElmerFEM will error out).
[x] Add unit tests for QElmerRenderer
[x] Update Gmsh/ElmerFEM installation instruction, and place them in the appropriate directory.
[x] Update ElmerFEM Tutorial to work with MultiPlanar class.
[x] ~~Add QElmerRenderer options to QAnalysis class~~

The current version of ElmerFEM will only support capacitance extraction analysis. Next steps will include adding more analyses, such as eigenfrequency extraction.
The assign_nets function inside QElmerRenderer works properly but probably needs refactoring since it inefficiently scans through different geometries assign nets and it has grown so much it makes the code difficult to read.
It has been decided to leave out adding QElmerRenderer to QAnalysis as part of this PR. This has to be done later on when LOM2.0 gets integrated.

qiskit-community / qiskit-metal