made some things in grammar optional

psGrammar/tasks/manipulation/manipulationTask.jsgf

 #JSGF V1.0;
 grammar manipulationTask;
 
-public <navigation> = (tobi | biron) [please] ( clean the <cleanShelf> | <table>);
+public <navigation> = (tobi | biron) [please] ( [clean the] <cleanShelf> | [clean the] <table>);
 
 <cleanShelf> = (shelf);
 <table> = (table);