Fixes #12364 - Use NPM+Webpack to handle external assets

This commit introduces NPM and Webpack to handle external assets.
It also provides ES6 support and a live reload dev server that can be
used by running `foreman start` instead of `rails start`.
Do not forget to run `npm install` before starting the server....

Fixes #8797 - Separate style from the HTML in emails

By using roadie-rails gem (1.1) style can be separated from email
html foramt, and absolute paths can be used.
style was separated to 'email.css'

fixes #14318 - load JS translations table for current locale only

Fixes #13235 - content from application layout extracted into a partial

Fixes #9480 - multiple NICs integration with compute profiles

From users point of view:
- interfaces setup in compute profiles is back
- interface related compute attrs get merged into host NICs upon compute
profile selection
- NIC overview table displays details in the column "Type"...

fixes #8802 - add Turbolinks support

Fixes #5139 - leftovers subscribe_to_all_hostgroups

Remove user_xxx unnecessary tables and notices

Update subhostgroups removed

Fixes for migration of foreign keys

Remove users from compute_resource fixture

Remove table notices after fk are removed for pg/mysql

fixes #3935 new login page RCUE style

fixes #3811 - merge with new layout

Fixes #3811 updating to bootstrap 3