Metaclass factory to replace Registrar and registry access classes

[cczhu]

We currently use Registrar metaclasses to register different analysis classes in CountMatch. There are multiple metaclasses, but all share nearly identical codebases, so it would be ideal to be able to write something like

DV_REGISTRY = {}
"""Dict for storing derived value processor class definitions."""

DVRegistrar = RegistrarFactory(DV_REGISTRY, "DV_REGISTRY", "_dv_type")

in place of the current DVRegistrar definition.

Ditto for DerivedVals:

DerivedVals = RegistryAccess(DV_REGISTRY)

Tests should remain the same, since the functionality is identical. Thus, very little effort wasted when writing tests currently.

[cczhu]

Also, in the tests, move Registrar class tests into the same class as launcher tests.

[cczhu]

Also, the neighbour module needs a metaclass registrar and a functional wrapper for initializing nearest neighbour calculator instances.

Once you've built this registrar, change the relevant test fixtures and preprocessing functions in test_matcher.py as well.