v2.0.0: 9600, 300 Baud modems and FX.25

Added:

• 9600 Bd G3RUH modem
• 300 Bd Bell 103 modem
• FX.25 (AX.25 + FEC) support - fully Direwolf and UZ7HO compatible
• and other changes and fixes

See CHAGELOG.md for details.