Smarter Statistics Updating

[fhats]

Statistics don't need to clear the whole container div every time an update is received. Hold on to the current stats that generated the page and compute some kind of lazy 'diff' to tell what needs to be cleared. Additionally, only grab stats if the 0th track in global play queue has changed (i.e. the current track is changing) as this is the only action that will cause a change in statistics. This can probably go for history as well.