Because of the way ExtractPaths works, `params[:format]` wouldn't
necessarily be available at the time this filter was running, and so it
would erroneously redirect to `new_user_session_path`

Handles stuff that's shared across admin controllers.

That was the only place it was used.

As a last resort it was calling a method that didn't exist. Woops!

Replaces two calls that this method simplifies

Merge branch 'master' into non-interactive-aws-install

Conflicts:
	doc/installation.md

Fix merge mess in installation.md

Didn't bother with files in db/, config/, or features/