0.3.0-alpha 2022-10-27 BEACON HUT

Changes:

• Open source!
• PDS4 importer with proctools
• Ad-hoc Spectrum viewer in canvas
• Significant rewrite of expression execution code, permitting custom
  types to have operations defined on them
• Direct input method for library use
• Improved default RGB mapping in canvas
• Testing
  • Basics testing
  • Testing of the operating principles (see Principles)
    • Source rules
    • ROI rules
• rect node can now be edited numerically
• circle node can add circular ROIs, which can be edited numerically.