Function to return type of representation

[antirotor]

[!NOTE] This is part Representation Schemas Epic effort

We need function in the core that will check wheter the representation is new style traits based or old style. This function should be then used down the line in the pyblish plugins to determine their compatibility with new style representations so we can fork the logic inside.

This needs to be created in the core so if the way how we define representation changes, we won't need to refactor it in many other plugins.