Allow users to change style via style parameter by default

Currently, only admin users can use the style parameter for quickly changing the board style. Users have to go through the process of entering the ucp and changing their style there. Previewing styles is not possible for them.

This however also prevents us from being able to use extensions like a stylechanger.

As there is no point why users shouldn't be able to use something like a stylechanger, this behavior should be changed.