Update sync icons, new multiplayer toolbar button

The multiplayer toolbar button is the same globe used for the
multiplayer option on the title screen, since it seems like
a nicer (and better?) looking option than the two riders.

Also conflicts less with the new sync icons.

resources/g2/sprites.json

@@ -418,6 +418,11 @@
     {
         "path": "icons/map_east_pressed.png"
     },
+    {
+        "path": "icons/multiplayer_toolbar.png",
+        "x_offset": 0,
+        "y_offset": 0
+    },
     {
         "path": "icons/multiplayer_sync.png",
         "x_offset": 0,