Update to new version, minor enhancements:

• Added experimental strobe disc display.
• Gauge has a quicker and more damped response.
• Main window resizing aspect ratio unconstrained.
• Adding target frequency in spectrum area as a vertical blue line.
• Config files moved to JSON format.
• Added persistent UI settings in JSON format.
• Added experimental liblingot core library.
• Note names can be read from comments in Scala .scl files.
• Code improvements and compliance with stricter C standards C99, C11 and C18.