New -port command line parameter

This merges both -clientport and -udpport command line parameters into a single -port parameter. As it was redudant having two parameters that does the same thing. Partitally untested, as I have no idea if hosting or joining a server using a random port works. But I do know that the master server doesn't like port numbers past 9999 (Which in most cases the random port number assigned by the system will end up being in the five digit range), and will refuse to add the server to the list.

This is also a prerequisite to UPnP support rewrite.