demoChallnge grammar: grasp object added

pocketsphinxAdapter/grammar/demoChallange/demoChallange.jsgf

 #JSGF V1.0;
 grammar ToBI_demoChallange;
-public <statement> = [tobi] [please] (<followMe> | <stop> | <cleanUp>) [please] [tobi];
+public <statement> = [tobi] [please] <command> [please] [tobi];
 
+<command> = <followMe> | <stop> | <cleanUp> | <grasp>;
 <followMe> = follow me;
 <stop> = stop [it];
 <cleanUp> = clean [up];
+<grasp> = grasp [object];