Migrated Drawing to unified api

- Cast from nfloat to float
- Change RectangleF.CGSize to CGRect.Size
- Changed CGContext.SetShadowWithColor to CGContext.SetShadow
- Changed float[] being passed as method param to nfloat[]
- Changed Spot.CGPoint to Spot.Point
- Replaced MonoTouch.Foundation with Foundation. in designer.cs files