Be able to set default room properties from the admin console

Committed a new admin page to setup default groupchat room properties. These properties are used if a room is created via XMPP (not via admin console).

If you want create a new room via admin console and you have multiple groupchat services, I can't know which default properties do you want to use. So I thought maybe we reactivate the muc.room.maxUsers, etc. properties to setup the admin console?

This ticket duplicates the issue.