Updating tests.

Adding several methods to SateTestCase. I have consolidated two
methods, '_main_execution' and '_exe_run_sate' from test_main.py
and test_run_sate.py, respectively. These now provide two ways
of executing a sate run from an instance of SateTestCase. I have
also added a third method '_exe' that runs sate "internally" by
simply calling 'sate_main'.

Also adding several housekeeping methods to SateTestCase that
now allow full runs of sate (via '_exe', '_main_execution', or
'_exe_run_sate') to clean up after themselves.

Updating imports accordingly.
Updating tests.

Removing several methods from test_main.py and test_run_sate.py
which are now consolidated into the SateTestCase class; imports
updated accordingly. These changes along with those in the previous
commit allow the exhaustive tests in test_main.py and test_run_sate.py
to clean up after themselves.