Escape URLs when adding them into the queue (sabnzbd/sabnzbd#73)

My instance of SABnzbd isn't escaping URLs to NZBs that are added from
3rd party clients. Escaping them before adding them to the queue seems
alright to me, which then trickles that data over to the
sabnzbd.urlfetcher as it's needed. It also seems to have the effect of
displaying then properly in the Queue UI.