Add Initial Drawing States

[mohamedAdhamc]

Currently there is only one active state which is the state for drawing freely on the canvas. there should be at least two more initial states:

1- Circle
2- Rectangle

This entails:

1- Changing the bottom toolbar to use some sort of "radio buttons". i.e. only one pressable at a time.
2- Pressing the button sends a signal which is caught from the canvas which updates the internal canvas state
3- Updating the canvas paint event handler to work according to state. Also probably need to do the same for the mouse events.