Refactor song selection across the app

- Added a new SelectedSongs service. Its purpose is to store an array of selected songs and all behaviour associated with it : adding songs to it, removing them, toggling a song, etc. It also changes each song's selected property.
- Removed selectAll, selectNone, playAll, playFrom, addSongsToQueue and selectSong from main-controller.js. Those are now defined either in queue.js, subsonic.js or archive.js, depending on where they are used. I know it does add some duplication between archive.js and subsonic.js, but this will be addressed in a later commit (maybe by creating a shared service).
- Refactored subsonic-service.js' addToPlaylist() and split it between subsonic-service.js and subsonic.js (like all the other playlist-related functions).
- Moved subsonic-service.js' songsRemoveSelected() to subsonic.js since it only removes songs from the scope.
- Removed $rootScope and utils (unused dependencies) from subsonic-service.js

app/queue/queue_test.js

@@ -2,12 +2,14 @@
 describe("Queue controller", function () {
     'use strict';
 
-    var player, scope;
+    var player, scope, SelectedSongs;
     var song;
 
     beforeEach(function () {
         module('jamstash.queue.controller');
 
+        SelectedSongs = jasmine.createSpyObj("SelectedSongs", ["get"]);
+
         inject(function ($controller, $rootScope, globals, _player_) {
             scope = $rootScope.$new();
             player = _player_;
@@ -15,7 +17,8 @@ describe("Queue controller", function () {
             $controller('QueueController', {
                 $scope: scope,
                 globals: globals,
-                player: player
+                player: player,
+                SelectedSongs: SelectedSongs
             });
         });
         song = { id: 7310 };
@@ -62,7 +65,7 @@ describe("Queue controller", function () {
     it("When I remove all the selected songs from the queue, it calls removeSongs in the player service", function () {
         spyOn(player, "removeSongs");
         var secondSong = { id: 6791 };
-        scope.selectedSongs = [song, secondSong];
+        SelectedSongs.get.and.returnValue([song, secondSong]);
         scope.removeSelectedSongsFromQueue();
         expect(player.removeSongs).toHaveBeenCalledWith([song, secondSong]);
     });