Fixes #5821 - Capsule Content API/Backend
Fixes #5821 - Remove the fort engine

The code now uses mainly the Foreman's proxy logic + additional
support in Katello itself: not need to maintain separate engine just
for the node syncing
Fixes #5821 - address PR review issues
Fixes #5821 - add tests for capsule related features
Fixes #5821 - fix binding repository to the node
Fixes #5821 - add capsule content authorization
Fixes #5821 - add capsule content authorization tests
Merge pull request #4118 from iNecas/capsule-api

add capsule support to API/CLI