ivory-px4-hw: refactor MS5611 into reusable components and test
ivory-px4-hw: add HMC5883 I2C driver
ivory-px4-hw: ms5611 test cleanup wibbles
ivory-px4-hw: mpu6k test cleanup wibbles
ivory-bsp-stm32f4: i2c tower tracks invalid (dropped) requests
ivory-px4-hw: trivial hmc5883l test (not working yet)
ivory-px4-hw: BUG HOTFIX: px4-ms5611-test fails without uart driver built in as dead code!

* going to have to circle back and figure this one out, but the reasons have eluded me so far
ivory-bsp-tests: remove MPU6000 test, subsumed by ivory-px4-hw's mpu6000 driver

I dont want to maintain the same code in two places.
rename px4 test apps w/ px4 prefix, not bsp
ivory-px4-hw: remove comments in px4-mpu6k-test app

 - this app confirmed to work properly with and without uart included
ivory-px4-hw: hmc5883 test works when i2c address corrected

* messed up the shift down by two when translating from spec