Support for MAVLink v2.0

[Cride5]

Add support for version 2 of the MAVLink protocol.
Will require changes to parsing and implementation of v2 handshaking.
Details here: https://mavlink.io/en/mavlink_version.html

[petergerten]

@Cride5 did you look into implementing mavlink 2 support? I am very interested in it as well.