Merge pull request #3864 from RosettaCommons/roccomoretti/multi_unit_run
Fixes/additions to the unit test running script.
* Parallelize the test discovery phase, to reduce lag before actually launching the test
* Allow users to specify multiple unit tests to run on the command, a la integration.py
* Convert the -1 option from a test specification option to a running mode option (the current ways of using run.py should transfer.)
* Adjust the mute defaults such that we mute by default unless running a single test.
* Adjust timeout such that it's turned off when running explicitly specified tests
* Change things such that you use the same Python for scons path introspection as you're using to run the script.