Several solr changes [MJ-921]

Done:
- Add second collection
- Add fields to schema
- Add/delete from both collections where appropriate

In progress:
- Deleting docs from the _current collection that are older than 30 days
- Dashboard searching
- ...

All tests pass.
Opinions, does this need to be its own task? I call delay() at the end of read_new_logs, but this is small enough that it's probably not necessary.