Fix the Play button.

- Use playpause() instead of play() on the Play button.
- Add 'Cache-Control' response header to answer firefox's duplicate GET's.
- rbplayer.js: reload() page after play_queue/<id> to re-start updateTimer.
  Nokia browser doesn't trigger a pagechange event when the queue_popup is
  closed, so we force one to restart the updateTimer.
Add preferences dialog for setting webserver ip address and port
Merge branch 'preferences-dialog'
Preferences dialog has been tested works OK.