Simplify iframe modeler listening of play/stop events

[#64752200]

.addDispatchListener() was unnecessary in this case.
External model experiment: add listeners before iframe phone is initialized

[#64752200]

To be 100% correct.
Also remove comment which no longer is true, as now iframe modeler
won't send 'listenForDispatchEvent' message.
Add interactive presenting JSmol model (in iframe)

[#62565148]