Add an inference test and fix a filters test
Add support for e.g. "AnaSa"
Add extra tests for filters
Fix definition of 'samyogapurva'
Clean up some code and remove 'vibhakti' tests
Add more advanced utsarga-apavada detection

Originally I set out to solve just the issue between 6.4.77 and 6.4.88,
but this issue touched so many parts of the system that it was hard to
change just one part of it. Along the way, this commit adds some new
tests for filters and U-A inference.

About 80% of the tests pass.
Add support for e.g. 'corayati'

Still to-do: disambiguate between roots in the 'cur' gana and roots
of identical form in other parts of the Dhatupatha.