Add images and sounds in a useful manner

[RobinMeles]

For example we can at certain occupation levels or queue lengths.

[RobinMeles]

We could check the exercises from the BlueJ book. There was a MP3-player exercise we could check for the sounds.

[JoeyBB91]

This issue contains a somewhat duplication of the description for issue #9.

[JoeyBB91]

I have a few ideas for this issue:

• We could play a sound when the user is prompted when exiting the simulation;
• The same can be done for resetting the simulation.

For more info, see issue #9.

[koenhendriks]

Fixed in merge #46