Docs:
* Don't advertise services whose support is broken in Adium with no fix in sight.
* Instead, add a list of third-party protocol plugins.
* Minor tweaks.
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">