Restructure/revamp tests

The current tests have grown historically and their current structure is very confusing.

For example, MollomAccessTestCase contains a test to check the module behavior for invalid API keys, but also tests for administrative access permissions to Mollom's configuration pages, but also a test for the 'bypass access' property of Mollom-protected forms.

Additionally, many tests are relying on Comment module to perform other tests.

This means that it's not only hard to figure out where to add further tests (or to search for an existing), but also, makes it hard figure out what exactly is wrong in case of failing tests.

I want to suggest to re-order and re-structure the tests. Basically:

- API keys
- Server communication
- Module administration
- Form configuration and processing
- Reporting
+ various low-level XML-RPC tests

Perhaps more. Perhaps this suggestion is also wrong and there is a better structure.

Let's discuss.