Further updated commenting and functionality

Commenting still not fully formatted. Code is still brittle...
Redundant code still present in some methods.
Code should work, apart from issues listed below:

Incomplete methods
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DepartingTrain.java:
addCarriage (DOES NOT CHECK FOR CORRECT TRAIN ORDERING YET)
DepartingTrain (not sure how to 'construct' empty train, that's already
declared...)
(Various error checking throughout methods still incomplete)

PassengerCar.java:
PassengerCar (error checking incomplete)
(Various error checking throughout methods still work in progess)

FreightCar.java
FreightCar (error checking incomplete)

RollingStock.java
RollingStock (error checking incomplete)

Locomotive.java
(Various error checking throughout methods still incomplete)
(Redundant code needs to be removed and formatted to match JavaDoc)