Finish implementing search

[eevee]

trafficstars

• [ ] Figure out how to make multiple schemata work in one index
• [ ] Figure out the problem of e.g. code needing different tokenizing than prose
• [ ] Add a hook (not an event hook surely? what then?) for loaded plugins to expose indexable content types
• [ ] Add automatic indexing and reindexing, probably via SQLA decoration
• [ ] Figure out some way to automatically reindex everything, maybe via an admin/stats page