Implement free text searching in addition to menu driven

[dpsnowden]

We need a little more thought on what we're searching for and how. Some options:

1. Free text searching all indexed fields
2. faceted search across variables, agencies...
3. ?

[lukecampbell]

In order to have this not burden the application backend we should look at changing our data model to have attributes for facets and tags.

This would be a good compliment to #178 I think. PostgreSQL has extensions for Lucene Full Text Searching. And adding faceted search wouldn't be that challenging, I think.

[lukecampbell]

We implemented a first pass at text searching but after the migration to PostGIS the text searching will be better, I think.