Added customer's ability to transfer between their own accounts, and
request deposits into other accounts.
Added functionality for Tellers to Get a list of requests, and respond
to them.
Set interaction with instantiating a new Transaction and appending it to
the global transaction list.
Gave requests a boolean field to mark whether they're approved or not.
Added into constructor the function that adds them to the global request
list for use by tellers.
Added Functionality for Requests for tellers to get, add, and approve.
modified constructor so that when an account is opened, it's added to
the customer's list of accounts automatically.  Also added Request
functionality, to see what pending requests for the account there are
for the customer.
implemented the interface, which applies to all acounts except LOC and
loan, allows the customer to directly withdraw an amount from the
account.
implemented CustomerTransferWithdrawal method for interface.
implemented Transfer between own accounts, and request Deposit method.
added interface CustomerTransferSource