Ability for admins to delete spaces

Now the spaces controller supports destroy (to actually delete) and disable (to disable like the old destroy action did)

Actions are authorized by cancan and new tests have been added. The admins of a space can disable it, but only an admin can destroy
Space count in managing wasn't counting disabled spaces
Merge remote-tracking branch 'origin/branch-v2-delete-stuff' into branch-v2
Overall improvements on disabling and removing spaces

Better icons for disable/enable, clearer messages and confirmations when a
user is disabling/enabling a space, and a general code review.

After merging branch-v2-delete-stuff

refs #1153