Engine: Initial work to allow Katello to be loaded as a Rails engine
alongside Foreman and be able to access the Foreman application.

Note, this does not enable any UI/API capabilities, the scope of this
initial commit is to get Katello's dependencies loaded and Foreman
running with Katello as an engine mounted.
Merge pull request #3173 from ehelms/engine

Engine: Removing rabl restriction to let Foreman proper handle.
Engine: Allow Katello::Engine migrations to run from Foreman db:migrate
Engine: Remove all existing migrations
Engine: Migration to add all Katello tables except users table to Foreman app
Engine: Add Katello specific user fields to Foreman users table
Engine: Updating pathing for namespaces in manifest files.
Engine: modify user to be extension of core ::User
Merge pull request #3178 from isratrade/schema_migrate

Katello::Engine migrations
Merge pull request #3180 from bbuckingham/engine

Engine: modify user to be extension of core ::User
Merge pull request #3182 from ehelms/engine-namespace-javascript

Engine namespace javascript