Added in support for changing priorities on the fly.  Forgot you could do that.  Added partial handling of roster events.  Took out temporary hack to clean up roster on login.

git-svn-id: http://svn.igniterealtime.org/svn/repos/wildfire/trunk/src/plugins/gateway@5101 b35dd754-fafc-0310-a699-88a17e54d16e