WorkUnit Prefactoring

[jeremykubica]

This PR does a bunch of prep work before making run_search.py take a WorkUnit as an option. The goal here is to make that later PR simpler and more readable.

Changes include:

• Remove Interface class from data_interface.py and add an option to load directly from the configuration file.
• Add the ability for the FakeDataSet to save to a WorkUnit
• Remove a bunch of unneeded parameters being passed to do_gpu_search
• Instead of computing (and then possibly overwriting) suggested_angle keep the data in the configuration’s average_angle parameter and only overwrite if needed.
• Move find_sigmaG_coeff out of PostProcess class and make it a standalone function.

Most of the diff lines are the result of removing the Interface class and the resulting changes in indentation.

[maxwest-uw]

nice!