Degeneracy checking for MF-TEMPO

[piperfw]

Make use of the degeneracy checking introduced by #113 in MeanFieldTempo / MeanFieldTempoBackend.

This calls BaseTempoBackend from MeanFieldTempoBackend with the optional unique=True and degeneracy map, dimension arguments for each mean-field system.

Coverage and physics tests for mean-field with degeneracy checking (unique=True).

Other changes:

• Added ValueError checks in tests/coverage/tempo_parameters_test.py to improve coverage of tempo.py (this is now close to 100%; the missed parts are the use of the optional backend_config argument - which would require more extensive parsing if tested)
• Bath now has acomm and comm properties for coupling operator anticommutor/commutator diagonal elements, rather than these having to be re-created in tempo.py
• [style] use np.ones instead of [1.0] * num to create constant arrays
• [style] had to disable too-many-arguments in pylintrc as number of arguments for MeanFieldTempoBackend now exceeds 15 - we should probably look to consolidate this at some point
• added assertions in BaseTempoBackend to check degeneracy maps and dim are supplied if unique=True. This is not user facing i.e. just to help developers - happy to undo this

[gefux]

Sorry for the delay. Thank you for also tidying up a few things on the way!