Add crash recovery mode

[mriale]

Some crashes can be trapped and backups can be made of the image being edited.

On a crash, attempt to:

• Save the current image
• Save the spare image
• Save an error report
• Save additional information:
  • color depth
  • cycle info
  • screen mode

On a restart, check for crash info and attempt to:

• Restore images
• Restore additional information
• Ask if user wants to submit a crash report

[mriale]

Submitting a crash report would require a web back-end to receive the reports. I am not going to implement that at this time.