initial creation of method for field expression.
+test
added the narrow expression method.
+test
added natural number basic type.
added the post/pre op expression method.
+added the needed keywords to table.
+started the OperationDefinition.
added the bindingsNpp visitor class to handle bindings.
move the type binding to the appropriate visitor.
+make needed changes to the methods in the expression visitor.
move the SetBing to the Binding visitor and made needed changes.
+changes to methods in the ExpressionNpp to meet the move of the SetBind
removing comments that was not neccesery.