Make type registration dynamic

[candycode]

Currently all the available types are pre-created statically when a context is created.

Move to a fully dynamic solution where types are added at run-time by specifying QArg and LArg constructors together with the type to add as done in QPy.

Steps to implement:

1. Move QArgConstructor and LArgConstructor to separate include files
2. Move QArgWrapper and LArgWrapper into a separate include file
3. Change name of LuaArguments.h to LuaDefaultArguments.h - these are the types registered
   by default
4. Make GenerateQArgWrappers and GenerateLArgWrappers private members of LuaContext
5. Create a map between type names and *ArgConstructors to make it possible to check if a type conversion is supported and to retrieve the proper constructor given a type name

Note that (4) is required to access the type->constructor map declared as a private member of LuaContext