Visibility annotations should be checked and corrected as needed

[jbphet]

In #8 the code for this sim was modified to be in ES6 style. When this was done, the sim started failing lint due to a lack of visibility annotations. It's been a long time since I did any work on this sim, so it's not fresh in my mind, and it may never see the light of day again, so it didn't seem worth the time and effort it would take to make sure that all of the visibility annotations are correct. So, I just marked anything I wasn't sure of as @public and added a TODO to the corresponding file. This should be fixed up if and when this sim is revived.