LuaD enhancements

Fixed static arrays.
Fixed support for calling functions which receive const args.
Rework struct to use userdata; conversion is not lossy, conversion should be faster, less garbage, supports more features (methods, properties).
Classes improved to support fields, properties.
Static type interfaces and creation of struct instances in Lua code.
Default construction is supported in static type interfaces in lieu of a constructor.
I was just sticking with the established convention already present throughout the codebase... do you want me to change everywhere I encounter?