Add command "charge" to charge up the rover's energy store

proto/rove/rove.proto

@@ -65,6 +65,7 @@ message Command {
     // "move" - Move the rover in a direction, requires bearing
     // "stash" - Stashes item at current location in rover inventory
     // "repair" - Repairs the rover using an inventory object
+    // "charge" - Waits a tick to add more charge to the rover
     string command = 1;
 
     // The bearing, example: NE