Allow queries to filter based on subannotation properties

[MichaelGoodale]

Right now it would be nice to be able to filter queries with subannotation properties, for instance, making a phone query that only included VOTs with a confidence of a certain amount.

[msonderegger]

@MichaelGoodale yes, definitely.

I think this may be possible already in polyglot but isn't in the iscan interface?

[MichaelGoodale]

So there was a (very) small error in the front end that prevented making filters based off subannotation properties that I've since fixed. However, the actual filters don't seem to work beyond say, "confidence != 3", I can't for instance, do "confidence < 50" or something like that. I'm not entirely sure why but I know the issue is around here although I'm not sure how to fix it. Maybe @mmcauliffe could take a look at it

[MichaelGoodale]

This was accidentally closed in my commit, I had meant to close #209