pymavlink: fixed modes on hexa, octa etc
message_definitions: added health sensor bits as enum

thanks to Randy
pymavlink: initial support for parsing dataflash logs
rotmat: added support for equality testing to Vector3()
mavextra: added a simple DCM gyro propogator

useful for analysing DCM failures
pymavlink: added support for text dataflash logs

useful for APM2 text logs, allowing them to be used with mavgraph
pymavlink: support flightmode in DFReader
release pymavlink 1.1.8