Move add/update channel logic into a re-usable method

[saltybeagle]

Once you get too many channels, you're going to hit

Too many open files in pearhunt/scripts/rescanChannels.php on line 10

We need to move the logic for updating channels into methods so they can be re-used without including the file again. The logic should be inside some class files so we can start adding a web-interface to add channels or support ping-backs for updating channels remotely.