add & launch `bosch_imu_driver` on hardware

[rursprung]

the simulated IMU has already been added, but we haven't added the hardware driver for our Bosch BNO055 yet.

since the driver isn't released through the ROS infrastructure we instead have to pull in the git dependency directly.

[rursprung]

@joel5399: when testing this please make sure to follow these steps:

• delete the currently cloned bosch_imu_driver folder in the catkin workspace on the RPi (i manually cloned that on the RPi yesterday)
• update to the code from this PR
• run git submodule update to ensure that the driver is downloaded into vendor/bosch_imu_driver
• to verify: running rosdep install --from-paths . -i should then report that it can find all dependencies (i've listed bosch_imu_driver as a dependency of smt_launch_hardware)

as discussed, it could well be that we might need the fix from https://github.com/mdrwiega/bosch_imu_driver/pull/14, in that case i'll update this PR to check out that instead of their master branch in our submodule.