Tidy-up Advection class and subclasses

Issue/feature addressed

Several member functions apparently specific to the WeakDG subclass have been added to the base class definition.

Proposed solution

The following virtual functions (along with their public accessor) have been removed from the base class

• v_AdvectVolumeFlux
• v_AdvectTraceFlux
• v_AdvectCoeffs

Those functions have been made non-virtual and have been moved to the AdvectionWeakDG subclass as

• AdvectVolumeFlux
• AdvectTraceFlux
• AdvectCoeffs

The following unused function has been deleted

• v_AddVolumJacToMat

However, dynamic_pointer_cast is now required in the implicit compressible flow code base.

Additionally, relevant member variables/functions have been made public/protected/private as relevant.

Implementation

Tests

Suggested reviewers

Please suggest any people who would be appropriate to review your code.

Notes

Please add any other information that could be useful for reviewers.

Checklist

• Functions and classes, or changes to them, are documented.
• [ ] User guide/documentation is updated.
• Changelog is updated.
• [ ] Suitable tests added for new functionality.
• Contributed code is correctly formatted. (See the contributing guidelines).
• [ ] License added to any new files.
• No extraneous files have been added (e.g. compiler output or test data files).