Expose more full-text search controls to the API

[abargnesi]

Derived from #45 #47

The FTS search filter is used like:

http://next.belframework.org/api/annotations/values?filter={"category":"fts","name":"search","value":"mandible"}

http://next.belframework.org/api/evidence?filter={"category":"fts","name":"search","value":"Approved"}

The syntax for the full-text search filter passes through to the implementation:

• annotations/namespaces uses SQLite fts4 and wraps each word like *word*
• evidence uses Mongo FTS and is passed through unmodified

We should provide a consistent API across all FTS filters. This might include:

• Specifying AND (conjunction) or OR (disjunction).
• Wildcard search
• Exact match