Minor formatting changes
Change call from valid? to supported_method?

`valid?` was over-vague.
Put classification specific mixins in same namespace

"Impersonal" as a construct or "Irregular" aren't
features of LatinVerb, but of Latin.  Make naming
reflect that.
Shorten call to DefectiveChecker
ExtractClass:  PerfectTenseRemover

Put hairy logic in a class to its own
Move phonographia: not per se a verb concern
Refactor of TenseMethodApplicator

Break down the complicated logic of applying tense
methods into smaller classes.