Updating javadocs comments to match those in the supplied javadoc file f...

...rom the assignment

I just went through and matched javadocs comments and the equals signature to match that of the Thing42.java javadocs file Jody gave us.

I'm going to do another pass-through, just to make sure it's all matching up, but this should be the bulk of the work for that.

@SterL @stevilstick @JamieWohletz @moquin101 @Kimmsudenver @ericvangelder 
I left the "Accepts duplicates" portion on here, but I again would argue that it should be taken out to match the API specs