added clear all drawing feature

[RaviRanjan-11]

No description provided.

[stevelandeyasana]

I'm not sure this is the right approach. I would have thought we would want to simply remove all shapes and reset the undo stack. Undoing every operation could be very expensive if there are many operations, whereas resetting the shape and undo stack lists would be very cheap.

[asherxiq]

This is not a perfect solution. It does have drawbacks when a user does save the drawing response and then again loads on the draw view. Definitely there will be no undo stack, in that case, the solution doesn't work.