[x] Add the thread flag button and dropdown menu choices to every thread
[x] Hook up selection of the flag to a transaction that saves the thread in flagged threads in database
[x] Much like applications, a thread may only need to be viewed once for a number of infractions, so the flagged record should be able to be revived for consecutive calls for attention
Actually, multiple requests for review should be allowed because people may have different reasons for flagging that an admin might not notice unless explicitly labelled.
Blocked by #71 .