add debug png output to shrink wrap and clean up a bit
add debug png output to shrink wrap and clean up a bit

  - move first mask creation inside loop to reduce code duplication
  - add possible workaround for #40 (commented out because not tested enough)
  - add multiple png debug outputs to see what is done at each step
  - parallelize complex to float copy

ComputationalRadiationPhysics/imresh