Allow overwriting answers

[cgfm]

Added suport for overwriting the answers with msg.answer. msg.answer could be an array like ["a","b","c"]. Then the value (a,b,c) will be the returned payload. It also could be [ {"text":"a", "callback":"cA"}, {"text":"b", "callback":"cB"}, {"text":"c", "callback":"cC"} ] Then the callback will be returned. In that case only one out node will be displayed, exceped when timeout is enabled. In that case two nodes will be displayed.