Add nesting to facets in annotation filters

[tberardini]

Suggest a view that is not a straight list with more general classes at top but structured as a hierarchy instead. Can determine distribution of organisms with annotations, also figure out where specific species with not immediately identifiable names fall.

[kltm]

We need to port these tickets over some time, but this is a good place to hang them.
Duplicated in:
berkeleybop/bbop-js#30
berkeleybop/bbop-js#8
#84