Sort channels by alphabetical order & use groups

[fpoirotte]

To make it easier to find a channel given its name, I think they should be listed in alphabetical order.
However, to put some emphasis on "well known channels" (pear.php.net, pear2.php.net), I'd also suggest separating channels into two groups (using the HTML <optgroup> tag):

• "Official/supported channels" (that's where pear.php.net belongs for example)
• "User contributed channels" (eg. for other PEAR channels)