The projectlayer file dialog now accepts files with the extension
*.3dlp.zip and will extract the contents to a temporary folder. It then
finds any *.bmp files and adds them as a set of layers.

Notes:
- Offset works, but currently scale does not affect the bmp files.
- *.3dlp.zip was chosen to mark the file as being for dlp based
resin printers, but also processable by regular archive programs.
- Have also introduced a checkbox to let the user decide to display
  fullscreen or not, as they may want the window dragged to a second
  output.