Simplify search and use postgres FTS

fixes #283 on github.

Make tests more powerful and easier to use. There are no longer multiple
search runmodes, we are back to a single search bar. We're now
supporting searches of many of the text fields in the DB, which will all
resolve to their corresponding vendor.
Don't put pg fts fields on abstract models

because it breaks fixture loading. This commit fixes fixture loading,
and so re-enables the tests that use them.