Fixed L2norm for FilterError

Issue/feature addressed

The current implementation of the error filter computes the L2norm (of a 3DH1D expansion) in phys-wave space, which is mathematically incorrect.

Proposed solution

The L2norm should be computed in phys-phys space.

Implementation

If 3DH1D expansion is in phys-wave space (EquationSystem.cpp:809), converts the expansion into phys-phys space using HomogeneousBwdTrans in EquationSystem.cpp:812 before computing L2norms (EquationSystem.cpp:818-844).

Reverts the expansion into phys-wave space by performing a HomogeneousFwdTrans in EquationSystem.cpp:849.

Tests

I have added a test case that checks the output from FilterError in IncNavierStokesSolver_3DH1D_L2ErrorFilter using a series of regex commands.

Suggested reviewers

Jacques, Spencer, Henrik

Notes

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).