Make more widespread use of D20CAF type rather than just integers

[dolio]

This PR doesn't change any logic. It just tries to make using the D20CAF type better without circumventing type checking.

• It makes D20Actn have a D20CAF field for flags, rather than just an integer.
• It adds bitwise operations for D20CAF that maintain the type instead of auto-converting to uint32_t.
• It removes a bunch of casts that are unnecessary in light of the above two changes.

For python, I elected to keep things as integers, and changed the flags field to use def_property to do the conversion. This is because python enums don't work as well with flag types, at least in python 2.

The motivation for this was annoyance when porting more grenade functions, having to cast things back to D20CAF and whatnot.