What's new in this version:
• Greatly improved drag and drop, and copy and paste, for the project- and scene-panes (using concurrent background queues).
• Added and modified the 'New"-menu item under 'File'.
• Properly implemented the add- and remove-buttons for the project- and scene-panes.
• Many, many bug-fixes for crystal, molecular crystal, protein crystal, molecule, and protein.
• Updated for Swift 4.1.
