Ability to configure a file size limit for HipChat Server file sharing.

To reduce the strain on storage etc, we would like to have the option to configure a file size limit on file sharing.

This would be handy as we, at the moment, have only the ability to enable to disable file sharing.
At the moment, it's disabled, but obviously we see the benefit of having the ability to share files, but since it's a self-hosted version of HipChat and we have limited resources, we need to be able to control things like this.