Docker: Add environment check job between tests

* Generalizes output.OutputGoodBase into environment.AllGood

* Fixes up output.OutputGoodBase to use new general interface

* Preserves all existing interfaces

* Added standalone executable helper script that is able
  to send default configuration options through and execute
  any executable placed under the 'envchecks' subdirectory.

* Added envchecks/README explaining the (simple) requirements

* Added simple script to notify about unexpected images existing

* Updated control file to call run_envchecks.py script at the
  beginning and in-between every test.  Any negative results
  are reported, but non-fatal.

Signed-off-by: Chris Evich <cevich@redhat.com>
Docker: small environment cleanups

*  Updated documentation

*  Fixed a few docstrings / comment

Signed-off-by: Chris Evich <cevich@redhat.com>
Merge pull request #38 from cevich/check_environment

Docker: Add environment check job between tests