Queues

Queue Q = x0  x1  x2  x3 ... xn-1     n =  # elements
A queue is like a list but the nodes are only accessed first-in-first-out
or FIFO.

Functions:
createEmptyQueue()	returns a newly created empty queue
front(Q)   		returns the first node of Q
dequeue(Q)  		returns and removes the first node of Q
enqueue(Q, x)		returns Q with x added as the last element 
isEmptyQueue(Q)		returns true if Q is empty and false if it is not