Fixes #7214: add !optional to @extends, required after sass update

There were sass errors occurring on load after we upgraded sass.
This commit adds !optional to the @extends so we don't get an error.

http://projects.theforeman.org/issues/7214
Merge pull request #4600 from waldenraines/7214

Fixes #7214: add !optional to @extends, required after sass update
Fixes #7120/BZ980113: use BS3 on dashboard to make it responsive.

The dashboard was displaying badly in smaller browsers.  This
commit reworks the dashboard to use bootstrap 3 classes and
thus makes it responsive.

http://projects.theforeman.org/issues/7120
https://bugzilla.redhat.com/show_bug.cgi?id=980113