Adds a little button to the trusted domain warning, if an admin clicks on the warning he will be redirected to ownCloud and asked whether he want to trust this domain.
By far not the cleanest code, or clean at all, but does the job and I don't see a reason to make a lot of changes for this little improvement.
Currently it only allows the admin to enable or disable the HTTPS
enforcement, but in the future it could be expanded to further options.
The HTTPS enforcement only allows the admin to enforce it, if he is
connected via HTTPS. (To prevent admins to enable it without a proper
SSL setup)