-Added NetworkNode class to represent the base of both clients and servers

-Anything shared between the two, such as getIP() exists here
-Added simple GUI for clients. The way clients will work is that you can press "open" to select a file in your computer. When you do this, it should become available for every other client to select to get from you. There will be a list of all available files that can be retreived from other clients. Selecting one and pressing "get" will retrieve it. Currently, files can be selected and doing so should update a local list containing the filename and absolute path on the client and the hash table on the server of client IP and filename. The hashing algorithm has been implemented.
-Added two new classes FileHandler and FrameHandlerClient, used for setting up the GUI on the client and opening files. FileHandler could also be used when retrieving files