Annotated UnitTests run first in a particular TestCase

For any given TestCase, the unittests annotated with the @suite('unittest') decorator will be run before the other tests in that TestCase. One step closer to all unittests being run before all non-unittests!

Note: The plugins are under the unittest_annotation2.py name. I named it differently from INFRA-1346 pull request to avoid any merge conflicts. Eventually, they will be moved to one file.