Add a helper script to unlock ownClouds admin features

I agree that enabling ownClouds admin features by default could lead to many broken setups and useless issues. But on the other hand, if you create a user-account for a friend, you could quickly end up with a full disk because you don't have quota. It is much easier to fill a disk with files synced by ownCloud than a mailbox. Also, I would like to use the Bookmark feature of ownCloud. There is even a Firefox sync plugin!

This is a nice way to let experienced users decide if they want to take care of their setups.