Problem: regress.py lookup of executable directory is unnecessarily complex

[michael-okeefe]

Problem

The regression test file docs/examples/regress.py uses an unnecessarily complex mechanism to guess where the bin directory is for the ERIN executables. However, CMake is capable of providing this information to the file.

Potential Solution

Update regress.py to take in the path to the last built ERIN bin directory. Also, potentially integrate closer with CTest and ensure that regress.py is only doing things that CTest is not (mainly the regressions). These might be disabled with a flag, for example.