Pass recipient ids, not recipient objects

Also move toward passing recipient ids as the longs they were born as instead of going back and forth from Strings.

This could also tangentially solve most of the issues with recipients not updating properly since they were cloned and marshalled into a Parcel. And, most importantly, this is a net :small_red_triangle_down: diff.

Fixes #2233, as recipient objects including their photos are no longer put into a parcel.