This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
Also
- Significantly improved search ranking, title is treated most strongly
- Adds tag names to the index
- Run search re-indexer more aggressively
- Re-index topic and all posts on category change
