Temporarily hidden because of problems with changing defaults. We don't want to
cause network instability because we have thousands of new unstable routers
churning the network, and can't change their default settings.

In future, we should look at the user's network and settings, and try to have 
"smart" defaults based on a user-chosen profile, or based on net type - see
Connectivity.isConnectionFast().

TODO: Fix link for Preference headers