Break licence_details methods out into separate class
Break licence_details methods out into separate class

I'm not 100% convinced this is the right abstraction, but these methods
are complex and there's more than one of them filling up the controller
so they need to be extracted and refactored somehow. I'm going to go with
this abstraction and see where it takes me.

alphagov/frontend,alphagov/frontend,alphagov/frontend,alphagov/frontend