Custom enums and structs #842
Description
A lot of definitions uses custom decoding to store information which is only relevant for a subset of entities.
Sometimes it makes sense to store this in entity extras/params but other times when more complicated it should probably be stored in enums(data maps) or structs (attribute maps).
It's not clear what the difference is between entity attributes and attribute maps and what should be stored where as the index values are shared between all entity attributes.
Either way it would be good to setup an easy way of adding custom enums and structs for the cases where it'd be better to use.