Add option to prefer album artist when sending scrobbles

Fixes #274

src/settings/scrobblersettingspage.cpp

@@ -84,6 +84,7 @@ void ScrobblerSettingsPage::Load() {
   ui_->checkbox_love_button->setChecked(scrobbler_->LoveButton());
   ui_->checkbox_offline->setChecked(scrobbler_->IsOffline());
   ui_->spinbox_submit->setValue(scrobbler_->SubmitDelay());
+  ui_->checkbox_albumartist->setChecked(scrobbler_->PreferAlbumArtist());
 
   ui_->checkbox_lastfm_enable->setChecked(lastfmscrobbler_->IsEnabled());
   ui_->checkbox_lastfm_https->setChecked(lastfmscrobbler_->IsUseHTTPS());
@@ -108,6 +109,7 @@ void ScrobblerSettingsPage::Save() {
   s.setValue("love_button", ui_->checkbox_love_button->isChecked());
   s.setValue("offline", ui_->checkbox_offline->isChecked());
   s.setValue("submit", ui_->spinbox_submit->value());
+  s.setValue("albumartist", ui_->checkbox_albumartist->isChecked());
   s.endGroup();
 
   s.beginGroup(LastFMScrobbler::kSettingsGroup);

src/settings/scrobblersettingspage.ui

@@ -102,6 +102,13 @@
      </property>
     </widget>
    </item>
+   <item>
+    <widget class="QCheckBox" name="checkbox_albumartist">
+     <property name="text">
+      <string>Prefer album artist when sending scrobbles</string>
+     </property>
+    </widget>
+   </item>
    <item>
     <widget class="QGroupBox" name="groupbox_lastfm">
      <property name="title">