Masking Updates

Great app, but there are some issues with Masking I'd like to discuss:

• Please add mask scaling/positioning. The masks are all square shaped and can't be scaled/positioned which makes applying a mask to anything but a square image ugly
• Please add custom masks. I would love to load black/white or greyscale images to be used as a custom mask, this would allow me to be much more creative.

Thanks again for the great app.