Refactor MS5611 driver to use interface nubs for the I2C and SPI versions of the chip. This reduces the amount of duplicated code.
Use common, board-type-agnostic code to allocate the PX4IO interface.
WIP on MEAS bringup, ETS airspeed sensors should be operational
Don't build interface drivers we don't have config for.
Don't build interface drivers we don't have configs for. Make the interface drivers build.

Change the way we handle the prom buffer so that we can init the interface before constructing the driver.
Merge branch 'master' of https://github.com/PX4/Firmware into fmuv2_bringup
multirotor_pos_control: PID ontroller derivative mode fixed
Merged master
Renamed actuator_safety back to actuator_armed, compiling but untested
Merge branch 'fmuv2_bringup' of github.com:cvg/Firmware_Private into fmuv2_bringup
Merge branch 'master' of github.com:PX4/Firmware into fmuv2_bringup
Fixed compile error due to bad merge
More compile fixes
Got rid of useless orb_receive_loop, moved some helper functions
Just some reordering in commander
Some more commander cleanup, param update handling code was doubled
Default to 2000 dps for L3GD20
Improved comments
Fixed disarming bug, use flag instead of mode switch
sercon is only used by APM now