Add required rotation option to driver startup command and fix a couple of details in warnings/comments

change type mag_scale to type struct mag_calibration_s for compatibility with master (only noted this thanks to travis build test)

passthrough: stop commander s.t. it doesn't disarm. Unfortunately this makes it impossible to stop the no-SD-card beeping with the safety switch

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

The LED init and Buzzer init messages were only annoying and not helpful
on Snapdragon and SITL. Therefore they are replaced with only developer
printfs.

mavlink_receiver: only publish the distance measurement of the mavlink flow message on uORB if they are valid
On the snapdragon, optical flow is computed in a separate process and sent to the mainapp via mavlink. Distance measurements come from a range sensor and are already published on uORB.
Here we make sure that meaningless distance values in the mavlink optical flow message do not interfere with the ones from other sources.

This reverts commit 76df4ecf.

Adding additional changes to the legacy driver config files, originally in the non-legacy driver config files.

Adding new CMake config files which will be used to generate a build which uses the legacy sensor drivers.  This is only temporary until integration with the corresponding PX4 DriverFramework drivers is complete.

running gps command without parameters results in segfault
due to illegal access to unallocated memory

Signed-off-by: Nicolae Rosia <nicolae.rosia@gmail.com>

Improved reporting and logging of ekf2 status