Fix mapping software

[kcking]

The mapping logic seemed to have bitrotted since the last burn. With major help from @xian we were able to get it all working again.

• Add null to allowed values in mapper dialog entity select
  • Automatic reset to null was causing a RuntimeException
• Wrap webcam capture callback in globalLaunch
• Add F3D pixel count (400)
• Fix mapping file name sorting, was previously sorting per-directory
• allowOverwrite when saving pixel mapper images
  • Was causing RuntimeException when re-doing a pixel with OneByOne strategy after a LogN run