Rewrite to support AutoHoyKey v2

[laurence-myers]

Complete rewrite to support AHK v2.

• Store the MIDI device name in the ini file. Don't try opening the input if the device name doesn't match the stored name.
• MidiRules: the device argument is now the actual device index. (It was previously always 0)
• Tray menu changes:
  • Remove "ResetAll" and "MidiSet"
  • Rename "MidiMon" -> "MIDI Monitor"
  • Add option "Show on Startup". On by default. If off, will not show the GUI the next time the script starts.
  • Add a separator between standard AHK tray menu items, and script-specific items.
• Always show the GUI if no MIDI input device was opened.
• Lots of unnecessary code removed
  • Don't test ports
  • Only listen to normal MIDI message (no sysex, errors, etc)
• Add MaxLogLines option to .ini, controlling how many log messages are shown. Defaults to 10.
• Update README.md
• Add zero-clause BSD license
• Use tabs for indentation in all files. Add .editorconfig to help enforce this.

Fixes #7