Swap the libnnpdf profile for a python dictionary holding all relevant information

Created by: scarlehoff

This is a very small change, I've simply moved the get_\w+_path methods to a python class. This simplifies the code in various places and removes yet another dependency in libNNPDF. I tried to make it more or less similar to how it used to work.

This is quite small and self-contained. The choice of having the "profile-class" inside loader.py was due to being the only file that really uses it (uploadutil being the other one) but I'm open to any other options, I'm don't have any particular opinions about this, just wanted to removed the libNNPDF import.