Add features for properties exercise

[mikedamay]

See the properties exercise.

There 7 features required for the properties exercise:

1. If WeighingMachine.Units is not auto-implemented then the following comment should be made: "The appropriate form for a property such as WeighingMachine.Units which has no validation or other processing required is that for an auto-implemented property". - Approved with comment.

2. If WeighingMachine.DisplayWeight has a non-private set accessor then the following comment should be made: "It is not approprirate for a property such as WeighingMachine.DisplayWeight which simply returns a value to have a set accessor. That should be removed.". - Approved with comment.

3. If WeighingMachine.USDisplayWeight has a non-private set accessor then the following comment should be made: "It is not approprirate for a property such as USWeighingMachine.DisplayWeight which simply returns a value to have a set accessor. That should be removed.". - Approved with comment.

4. If USDisplayWeight.Pounds has a non-private set accessor then the following comment should be made: "It is not approprirate for a property such as USDisplayWeight.Pounds which simply returns a value to have a set accessor. That should be removed.". - Approved with comment.

5. If USDisplayWeight.Ounces has a non-private set accessor then the following comment should be made: "It is not approprirate for a property such as USDisplayWeight.Ounces which simply returns a value to have a set accessor. That should be removed.". - Approved with comment.

6. If WeighingMachine.TareAdjustement is not an auto-implemented property then the following commen should be made: "A succinct way of implementing WeighingMachine.TareAdjustment is as an auto-implemented property with a private get accessor". - Approved with comment.

7. If WeighingMachine.TareAdjustment is an auto-implemented property but the get accessor is non-private then the following comment should be made: "A non-private set accessor is not appropriate for WeighingMachine.TareAdjustment as the instructions stipulate that the value must not be available outside the class". - Disapproved.

See the boilerplate here. See the completed example here.