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Merge pull request #434 from CommitteeOfZero/magic_enum

Switch out implementation behind enum lua interface to use magic_enum instead of better_enum, which does not require declaring enums with a macro to create a special class, and works on native enum types.
Add templatized unary operator+ to convert enums to underlying type.
Allow TryGet to get enum types directly without needing to cast from underlying.

This change will limit the usable compilers to Clang, GCC and MSVC.