Starts file transfer when an item is added to the funnel and playback once the first item is downloaded.

Also:
- fixes an issue where the local music collection is not refreshed when the page reloads
- sorts and rebuilds the party collection when items are added
- fixes an issue with the funnel visualization

Jira issue: APPPARTY-48
Merge pull request #23 from eelcocramer/APPPARTY-48

Starts file transfer when an item is added to the funnel and playback on...