Fix const definitions for MOAICameraAnchor2D and MOAICameraFitter2D

CameraFitter and CameraAnchor consts were set in `RegisterLuaFuncs` instead of `RegisterLuaClass` like other classes.  This fix moves them to the correct method to make them accessible from Lua.
Merge pull request #947 from criptych/fix-camerafitter-consts

Fix const definitions for MOAICameraAnchor2D and MOAICameraFitter2D