Improve Functional Test Code Coverage

Currently, the majority of functionality of phpBB is not covered by the test suite. Therefore, when changes are made, it can be difficult to tell if some random feature is going to be broken until after the patch is merged and a bug report gets filed. We need to expand the functional test coverage of the phpBB code for any parts that cannot be Unit Tested (e.g. logging in/out, creating a post, testing permissions, etc.).