Clean up reading/loading configuration file

Antonios reported that following the examples/example_darm.py file results in an error. I tracked this down to when sections of a configuration file metadata or interferometer have keys/values then the reading of the configuration file fails.

Jamie suggested doing away with <string> is in <key> in favor of <string> == <key> as well as adding some additional context to the special cases with some comments.

In addressing these issues, I also felt as though the parameters were being stored in an inconsistent manner. Some as python lists and others as numpy arrays. For consistency, I switched over to python lists.