changed some system-group tests to rest/create systems
Adds rest methods for activation keys and system groups
Merge branch 'master' of https://github.com/RedHatQE/katello.auto into headpin-rest-systems

Conflicts:
	src/katello/tests/system_groups.clj
Merge pull request #758 from blrm/headpin-rest-systems

Headpin tests blocked, added rest implementation for system groups