api v2 root-node for single-object responses
API v2 - ping controller and /api/ping route
API v2 - fixing bad merge-conflict resolution

these files were moved:
app/views/api/v2/common/collection_resource.json.rabl --> app/views/katello/api/v2/common/collection_resource.json.rabl
app/views/api/v2/common/single_resource.json.rabl --> app/views/katello/api/v2/common/single_resource.json.rabl
API v2 - renaming common resource templates to match rendering.rb
this route is actually /status
API v2 - /api/status
API v2 - ping controller no longer extends v1 controllers

also included is optional root-node for single resource responses

Conflicts:
	app/controllers/katello/api/v2/api_controller.rb
API v2 - switch from templates inside templates to layouts
attempt at disabling headpin tests and fixing ping tests
removing minitest skips
moar tests!!
Merge pull request #3462 from komidore64/post-rebase-ping2

updates for v2 API and ping controller