[XML Markers] Add Code Generator for Enum Classes

[AsherGlick]

Enum classes do not exist in the prototype xml parser, an example of them would be Chirality.

Right now in the Cull documentation, which uses chirality as a type, there is no indication that the type is named "Chirality". Unlike filter types, it is possible for an enum type like this to be re-used. Possibly there should be a new field in the enum definition that says it should have a custom data type name and not be "Cull" but instead "Chirality". However currently Chirality is the only enum type so it might make sense to ditch this generator and convert Cull to a custom type.