Android: Clean up hardcoded platform names

The same kind of change as the changes made in the previous
commit, but this change is more involved, in particular because
of how SyncProgramsJobService was using display names as keys.

Source/Android/app/src/main/res/values/strings.xml

@@ -334,6 +334,9 @@
     <string name="continue_anyway">Continue Anyway</string>
 
     <!-- Game Grid Screen-->
+    <string name="platform_gamecube">GameCube Games</string>
+    <string name="platform_wii">Wii Games</string>
+    <string name="platform_wiiware">WiiWare Games</string>
     <string name="add_directory_title">Add Folder to Library</string>
     <string name="grid_menu_settings">Settings</string>
     <string name="grid_menu_refresh">Refresh Library</string>