The unit tests for reviewboard.accounts has grown too large to

properly maintain. Some tests were in classes they didn't belong in, and

many tests were missing. Merges also became more difficult.
This change splits the test suite into a file per suite. The code for

the tests have not changed, with the exception that the sandbox tests

for auth backends have been split into two suites (one for each form

that's actually being tested in that suite), and some tests being pulled

out of improper test suites and into proper ones (probably in the wrong

places due to merges and user-contributed code).

Unit tests passed.