[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.
Prefetched tags; better performance. Didn't bother adding another parameter to filter_partners since only 2 functions use it and the prefetching only happens on prm (ie not on partner library).