Initial removal of the dashboard extension.

Conflicts:
	.travis.yml
	changelog.md
Mock things that we're not concerned with.

In these cases, we only care that the method in Refinery that is directly
responsible for allowing a controller returns false and that the active
plugins list is populated with the plugins that we expect to test our
assertions.
Replaced the refinery.admin_root_path with refinery_admin_root_path.

The new method detects which is the left most tab for the user
and uses that as their backend route.  This is a little slower
but it means that we don't have to have a baked in root path
for the admin section.
Updated changelog with dashboard removal PR.

[ci skip]
Merge pull request #2727 from refinery/remove-dashboard

Removed the dashboard extension!