[Improvement] #135 [Feature] #131

[Improvement] #135:
Added a directive to handle the listing of tracks. This way it will be more maintainable. Implemented in the stream-, favorites-, tracks- and profile-view. Also made the play/pause icon only show when mouse pointer is over the picture instead of the whole li-element. It made no sense to show the icons when you could not execute the play/pause function.

[Feature] #131:
Added a link from the username in the track details to the user profile. Included in the above directive ^^