mollom.test should be in a subdirectory

I am working on improving the existing Mollom tests and adding new ones, but the current tests do not show up in the Simpletest web interface because they are in the wrong directory (they need to be in a 'tests' subdirectory for Simpletest to find them in Drupal 6).

The attached patch looks gigantic, but all it does is move the mollom.test file to a new 'tests' directory; there are no actual changes to the code ;)

The tests still don't show up correctly in Simpletest even after this patch, but that's a separate problem which I think is best handled with a followup patch...