[++] Re-written barebones Doubly Linked List
[++] Re-written barebones Doubly Linked List

I re-wrote Doubly Linked Lists using a Reference class, rather than a
dictionary. Much easier to manage (in my opinion).

Append is the same, other than the new reference being a Reference
rather than a dictionary.
Remove is much cleaner, works PROPERLY (finally), and has a more defined
role. It now only removes the (left\right)most value, depending on the
left parameter. Left is defaulted to False to simulate the most common
use of queues pop()
show renamed to reveal

nbness2/TradingCards