Enumeration Consistency

[Alex Shelkovnykov]

Currently we don't have much consistency in our use of Enumerations: some places we have Enums, some places we have case classes, and some places case objects. In some places, we use case objects and write our own String parsing code.

Ideally we would use one consistent system throughout. It looks like an overhaul to the Enum structure is on the way, but until it's out and until we're using that version of Scala, I propose we use the Enumeratum library.