Unlock Student permissions needed for Ad Hoc Spaces

The following Course & Account Permissions for Students are originally
locked and disabled. This commit unlocks them so they can be enabled.

* Manage wiki
* Manage course files
* Manage assignment and quizzes
* Manage all other course content
Hide the Start a New Ad Hoc Space button

... until it is ready for prime time
Merge pull request #161 from va7map/ad_hoc-perms

Ad Hoc Spaces: Mod permissions and hide button