Improved YouTube scrobbling

I listen to a lot of korean music on youtube, which follows very different conventions for titling their videos than most.  As an example, with the parsing that was in use, about 5-10% of this playlist was successfully scrobbled: http://www.youtube.com/playlist?list=PL6120C9A728700B13

I did a few things to take care of that problem:
1) edited the parsing code a bit so that it handles more complicated video titles
2) added a feature to semi-permanently store the title and artist if you add them manually (will work over sync too)
3) tweaked the popup in "unknown" mode to auto-fill the artist and track with some reasonable guess values, and to show the error given by last.fm (usually "Track not found")

This takes care of issue #160 and issue #151

Some details:
* There's a button in the options page to clear stored data if something is wrong
* Any connector can "opt in" to store manually added data, by sending a uniqueId along with the "validate" and "nowPlaying" messages
* Any connector can "opt in" to auto-fill the artist and track by changing their "nowPlaying" message (in the case of failure) to include validationFailed: true, artist: artist, track: track

feedback welcome