Redesign Party Mode Selection Screen and Main Screen (#917)

* Redesign party mode selection

- All party modes are shown at a glance as tiles with an icon and their name, sorted by their name
- The tiles look and behave like the theme buttons, the details of the selected mode (description, target audience, players, teams, microphones, author and version) are shown below
- Modes that need more microphones than configured are dimmed and can't be started
- Select with the arrow keys or the mouse, the arrow keys also reach the Start and Back buttons, a click on a tile starts it
- More than six modes are split into pages
- Icons for Challenge and Tic-Tac-Toe and a general icon for modes without their own
- Fixes the number of players shown for modes with a fixed number of players

* Highlight Sing and Party in the main menu

- Sing and Party are shown as two large buttons side by side above the other buttons
- Statistics, Profiles, Options and Exit stay in one row at the bottom
- Without a profile the missing profile warning takes the place of Sing and Party, because both are locked then, and looks like the other warnings

Output/PartyModes/Challenge/Themes/Default/Default.xml

@@ -8,6 +8,8 @@
     <VersionMinor>1</VersionMinor>
   </Info>
   <Colors />
-  <Skins />
+  <Skins>
+    <PartyModeIcon>PartyModeIcon.png</PartyModeIcon>
+  </Skins>
   <Videos />
 </root>