api v2 - systems actions

- [x] - create
- [x] - index
- [x] - show
- [x] - update
- [x] - destroy
- [x] - tasks
- [x] - add_system_groups
- [x] - remove_system_groups
- [x] - package_profile
- [x] - report
- [x] - errata
- [x] - pools
- [x] - releases
- [x] - activate
- [x] - enabled_repos
- [x] - refresh_subscriptions
- [x] - tests!!
- [x] - squash commits