finger tracking pan gesture recognizer.

panmove.cs

					//addtl info at https://github.com/johncadengo/JCWindowShade/blob/master/JCWindowShade/JCViewController.m#L137
					var dragging = false;
					contentView.AddGestureRecognizer (new UIPanGestureRecognizer ((pan) => {
						if (dragging){
							var origin = pan.LocationInView(View);
							Console.WriteLine ("dragging at {0}", origin);

							var translated = pan.TranslationInView(contentView);

							var cf = contentView.Frame;
							cf.Y = origin.Y;

							contentView.Frame = cf;

						}
						if (pan.State == UIGestureRecognizerState.Began){
							Console.WriteLine ("starting drag");
							dragging = true;
						}
						if (pan.State == UIGestureRecognizerState.Ended){
							Console.WriteLine ("ended drag");
							dragging = false;
						}
					}));