Refactor renameValues in bspMorphRetriever
Refactor again for more efficiency
Add mappings for morphRetrievers

Long wanted feature. Morph tagset can now define custom mappings to
handle to return values of morphological retrievers.

That way we can use different morph engines and map their output to the
terminology a morph attribute set uses, as long as we know the
terminology a retriever uses.
Add mappings to all morph atttribute sets
Update SG configs to use proper mappings
Merge pull request #298 from latin-language-toolkit/more_morph_flexibility

Mappings between morph plugin and morph retrievers