Open Solo 3.0.0

MODES: Add new ArduPilot flight modes to pymavlink

Several new modes have been introduced to the various vehicles supported
by ArduPilot since the solo was created.  This patch adds all those new
flight modes to the enumerations in this older version of pymavlink.
For ArduCopter, this adds support for the following modes:
- Throw mode
- ADS-B Avoid (not a user mode)
- Guided with no GPS
- Smart RTL