Adding formal exception handling
Added another Exception class: NegativeElevatorException

Refined the messages that are printed out for each custom exception so
the value in question is printed out along with the message.

Added some additional documentation. This is not meant to be an
exhaustive change. The modified classes were modified for one of two
reasons:

1) To explicitly state whether an integer parameter value is meant to be
zero-based or one-based
2) While working with the class, I noticed that some documentation was
missing
Moar documentation

All interfaces, impl objects, and factory classes are fully JavaDoc'd.
The jUnit tests and exceptions have been ignored because they are not
necessary. If that changes, we'll obviously have to add JavaDocs.
Merge branch 'master' into exceptions

Conflicts:
	pImpls/Elevator.java
	pInterfaces/ElevatorInterface.java

I think I accidentally merged the wrong way. Oops