Clean up test database after tests

Fixes #1064

- Updated grunt config for unit and functional tests to remove the test
database after each is run.
- Cleaned up a couple of issues with the functional tests that may have
been causing travis builds to fail randomly, including: the start page
is now `about:blank` instead of whatever page the last test suite left
off at, added some checks in the logout tests to ensure they're truly
independent of the other test suites.