Add tests that the DB constraint preventing multiple bounty acceptors is working for issue #62.
Add a database trigger that ensures a bounty can't have multiple acceptors for issue #62.
Use less awkward grammer to describe the tests on the DB trigger checking multiple acceptors on the same bounty for issue #62.
Remove debug code from the DB migration for issue #62.
Correct the type of error expected when a duplicate acceptor is assigned to a bounty for issue #62.
Update the DB structure file with the DB changes adding a trigger preventing multiple acceptors on the same bounty for issue #62.
Merge branch 'devel-single-acceptor-constraint'