Implemented simple discounts based on Facebook connections (likes, event participation etc.).
Did some further work on abstracting common parts in the discounts models code (more could be done).
Added the official Facebook SDK to install requirements.
Register Facebook discounts with admin and translation.
Merge branch 'feature/facebook-discounts' into develop

Conflicts:
	cartridge/shop/admin.py
	cartridge/shop/models.py
	setup.py