Added a module for extra drush commands specific to Springboard testing

This hidden module, when enabled via drush, adds the `sb-test-list` and `sb-test-run` comands, which can take either 'springboard', 'core', 'contrib', or 'all' as arguments, and will filter out the list of tests by using a blacklist file. This way we can run a subset of tests and ignore tests that are incorrectly failing or aren't useful to us.

````
drush @site sb-test-list springboard
````

````
drush @site sb-test-run springboard --xml=/tmp/testresults
````