Engine: Fixes #3323: Sync schedule initial conversion to engine

This commit includes changes to allow user to associate sync plans
to products.
Engine: Namespacing vendor assets to be congruent with regular assets.
Engine: fixes#3324: Content view definitions initial conversion

This commit contains changes to support the following:
- content view definition CRUD - including cloning, filters, filter rules...etc
- content view publish/refresh
- modifications to support async tasks via delayed jobs
- etc
Merge pull request #3236 from bbuckingham/engine-content_views

Engine: fixes#3324: Content view definitions initial conversion
Merge pull request #3229 from bbuckingham/engine-sync-schedule

Engine: Fixes #3323: Sync schedule initial conversion to engine
Merge pull request #3232 from ehelms/engine-vendor-assets

Engine: Namespacing vendor assets to be congruent with regular assets.
Engine: Updating katello reset DBS to only reset Pulp and Candlepin.

This will not reset the Katello/Foreman DB like it did previously. That should
be done through the normal Foreman setup. This could be moved out to a rake
task in the future, but for now this is a utility method when needing to
reset your development environment.
Merge pull request #3242 from ehelms/engine-reset-dbs

Engine: Updating katello reset DBS to only reset Pulp and Candlepin.
Engine: fixes #3257 - Katello seeds.rb is run by rake db:seed in Foreman app
Engine: fixes #3381 - change username/email to Foreman column names login/mail