This puts the OrderedEnum generic class next to where it is actually used. It
also refers to the recipe it is taken from on docs.python.org. I also took the
opportunity to give this a capitalized name (since it's a proper type).
This is not really critical since list(Type)[i] works just as well. This fixes
a couple other problems from the enum transition:
- The name of TYPES was not really consistent with its new role as an enum
type. Renamed this ImageType.
- Fix a rather egregious bug in embedart (undefined reference to Image).
