Fix bug so boundary condition reference file checks include ones for Dirichlet and Robin, previously only Neumann BC files were checked

Concentrate session and output files together, these will eventually be in one record, so UI should reflect that

Add handling of cases of implicit extra variables, ADRSolver special case where no extra vars, effect of MOVEMENTS, and homogeneous simulations, just missing effect of refinement

Change interface for validate, now accepts a solver type, other functions and tests changed accordingly

Refactor dataset decorator to only require function, previous optional solver type now required to be specified with declaration

- Add a dataset with function input file
- Add input supporting file property for objects
- Remove redundant tests, preferring DATASETS with pytest.parmaetrize over old fixtures
- Make parametrised tests easier to interpret by uising suitable IDs
- Add Acoustic Solver dataset

Also change behaviour of a validation boundary check -> previously all BCs in geometry must be defined in session -> now all BCs defined in session must be present in geometry

Add support for [...] in BOUNDARYREGIONS in session file, usually just C[...], add deprecation warning so users are aware