Resolve "Time bound pipeline search"

Closes #66 (closed)

Two new fields to searches:

• time_bound to express time (in minutes) of upper bound for search time.
• priority especially added so that if multiple searches are being sent to TA2 at same time, then short immediate searches (say 1 minute) can be queued before long searches (many hours). Shouldn't rely on calls arriving in order they were sent. Is probably generally useful guidance across searches.

These new fields are presently, and intentionally not set up as updatable, but that might be point of discussion.