Sensor drivers

These are sensor driver improvements / new laser rangefinder kindly contributed by the APM dev community.
@tridge This is a call we only should allow / do on FMUv3, because on FMUv2 the chip select line is on a different bus, which means this is will enable a sensor on a bus *different* from PX4_SPI_BUS_EXT when called on FMUv2.