Make a decision about the covered state on classical coins

[jbphet]

This was discussed with teachers and we have some open questions about this. Not sure about lower portion. Assigning to @arouinfar for follow up.

[jbphet]

I asked about this in today's design meeting, and the conclusion was that the coins should not be masked when moving into the test boxes for the Classical Coin case, but the should be masked in the Quantum Coin case, as they currently are. So I'll need to change the behavior of the Classical Coin case such that no mask appears on the coins in this case.

[jbphet]

This morning I pointed out the @arouinfar that the single coin is not masked for the quantum coin case during the initial prep-area-to-measurement-area animation. She believes that this is as it should be, since it is depicted in a superposed state, and asked me to leave it as is.

[jbphet]

@arouinfar - I've implemented the changes where the classical coins are no longer masked when traveling from the preparation area to the measurement area. It's available on main and also in a dev version at https://phet-dev.colorado.edu/html/quantum-measurement/1.0.0-dev.15/phet/quantum-measurement_en_phet.html. Please check out the behavior and let @AgustinVallejo and I know if further changes are needed.

[jbphet]

Reviewed in design meeting, approved for now (might change based on interviews). Closing.