Several solr changes [MJ-921]

- Add second collection
- Add fields to schema
- Add/delete from both collections where appropriate
- Deleting docs from the `current` collection that are older than 30 days
- Dashboard searching

All tests pass.
My view tends to be, adding the task invocation is pretty cheap in terms of code readability.  And sooner or later we're going to want to be able to manually trigger this.  So leave it a task.