Implementing MVC

While trying to seperate tools, I realized it would be very difficult to
keep the tools seperate and modular from the main activity or view class
if we don't loosen up the couping between the components. So, this is
the first step. This code refactoring is incomplete and has introduced
major amount of bugs back in.
Issue with the previous commit fixed

In the previous commit many bugs were introduced. The ones known to me
are :
1. The back button on navigation is non responsive
2. The path you are currently drawing was not visible untill you lift
your finger.

This commit fixes the 2nd issue.
Point Creation now possible

Functionality added : now touching any point and lifting your finger
back marks a point on the canvas.