[PD-699] made tag search dive into contact tags.

This makes it so that tags from contacts propogatae to the partner in PRM (but they aren't actually added to the partner). This also makes contact tags searchable in PRM, instead of just partner tags.
It would be prefetch_related. Do we use contact and tag information everywhere that filter_partners is used? If not, we'd want to refactor filter_partners to only include the prefetch if the data is used. It might be worth checking the number of queries being made, but it's probably not a big deal on single-partner detail pages.