Basically, update master server code to v2

Removes rooms, replaced with cv_advertise and "Advertise" on the host menu.

According to the new API, SRB2APPLICATION is sent instead of MODID. A contact
field was added, but there is no means of accessing it or setting it.

As a slight change, the server list will be populated even on an outdated
version of the game. (The new API was designed with this in mind.) The update
alert is still presented first of course.