#70 #68 Modified Button to extend Widget.  Extended GUI

Modified existing Button class to extend from Widget
Made GUI not extend Container so it can be the central point of access
for a GUI
Added methods to draw and process events for the GUI
#70 #68 Worked on implementing mouse click events

Added mouse click command to take an action when the mouse is clicked
Modified gui classes so they return a bool when processed.  This is to
indicate if an element was clicked.