Configure gyro hardware filter to 100Hz, increase loop rate to 1667Hz

Small PID change

Add comment about rates. Begin USB configuration.

Require disarm before arm. Verify ELRS checksum.

Final (for now) 5 inch tuning

More aggressive 5 inch tune

Tidy up. Remove nav related code, this can be tracked separately.

More on GPS and altitude hold

Add some build tools to gitignore and add flash commands to Makefile * for those if us who like to keep their tools close * convenience changes: - var for path to elf2dfuse - alternatives for tool paths used by sixtyfive provided as comments - two different flash targets

Add build info and tuning notes to README