Touchups to Caroline's New Object Code and Taylor's Old Object Code

Change all for loops that iterate over object properties
to use the 'for in Object.keys' method of property retrieval
based on
https://developer.mozilla.org/en-US/docs/Enumerability_and_ownership_of_properties.

Remove comments for self-describing code.

Move property initialization into the object's constructor
where possible.

Declare common object functions via the object's prototype
rather than in their constructor, based on this discussion:
http://stackoverflow.com/questions/4508313/advantages-of-using-prototype-vs-defining-methods-straight-in-the-constructor

Remove the List.clear function- in this case, just make a
new list.

Fix semi-colons after functions (Taylor made an oopsie w/
js syntax!).