Renamed Location to Position and added tuple shortcuts

[tzachshabtay]

1. Added tuple shortcuts (example below) for a more friendly API possibilties.
2. Removed the ILocation interface and renamed Location to Position.

So, previous code which looked like this:

obj.Location = new AGSLocation(100, 200);
obj.Scale = new PointF(2, 2);
obj.Pivot = new PointF(0.5f, 0.5f);

var x = obj.Pivot.X;
var y = obj.Pivot.Y;

Can now be written like this:

obj.Position = (100, 200);
obj.Scale = (2, 2);
obj.Pivot = (0.5f, 0.5f);

(var x, var y) = obj.Pivot;

[ghost]

Sorry if dumb question, why was ILocation needed previously anyway?

Oh, nevermind, have read the commit comment.