Mask does not scale properly on HiDPI or Retina display

[ustk]

@d-healey Strange... I just need masks and proper blur too at the moment. And those layer limitations are bad

Graphics in general is a point that people are still asking for improvement and I understand Hise is not meant to be a photoshop clone. But when you hit limitations... I'd like to re-use OpenGL as well but not confident enough to deal with plateform specific issues... Well, it's one or the other I guess