Logic needed for Probe Key Location Map

[terracoda]

Currently on the descriptionProperties branch, #299

I added a location map at line 84:

const probeKeyLocationMap = {
  homePosition: 'outside beaker, near pH meter',
  atBottom: 'at bottom of beaker',
  underDropper: 'just under dropper',
  underWaterFaucet: 'under water faucet',
  halfwayOpen: 'under drain'
  otherLocationNotInSolution: 'not in solution'
}; 

And a description at line 244:

  probeLocation(( probeDescriptor: probeKeyLocationDescriptor ): string {
    return 'Probe is ${probeKeyLocationMap[ probeDescriptor ]}';
  }, 

For the dynamic description to work, the sim needs some logic that identifies the probe's location. I am not sure how involved that might be. @jessegreenberg, could you comment when you have time.

These descriptions will relevant when we add an additional keyboard shortcut to cycle the probe through these key useful locations. The other "otherLocationNotInSolution" is a catch all for all other locations and needs to be discussed.

[terracoda]

Marking onhold for now.