Improve filtering functionality in tk.bio interface

[mbrush]

Finding the types of concepts and statements one wants is currently challenging. Some simple enhancements to filtering functionality that could improve this:

1. Fix Relation Filtering: This is a very valuable feature that is currently not working. Also, it would be nice if the user was presented with a dropdown of all relations used in statements in the table so they could select one or more to filter/facet on.

2. Fix Statement Filtering by Semantic Type: Also doesn’t seem to be working. e.g. after filtering to select Genes, statements that have nothing to do with Genes are still returned. I assume the desired functionality here is to return only statements where the S or O is tagged with the Gene semantic type.

3. Allow users to select multiple types when setting filters.

4. Allow filtering by source from within the concept and statement results tables. Currently filtering by source is only available outside the context of search results.

[RichardBruskiewich]

Enhancement #1 above triggers fresh API issues: see NCATS-Tangerine/beacon-aggregator#21

[RichardBruskiewich]

The semantic type filtering does seem to work but the text filtering does not. I will continue to investigate.

[lhannest]

@YinglunQ We can pair program this if you have any questions.