Move sensor tests into subfolder 'sensors'

CMakeLists.txt

src/tests/sensors/analog/test-analog-pressure-sensors.cpp

src/tests/sensors/analog/test-battery-voltage.cpp

src/tests/sensors/analog/test-current-sensor.cpp

src/tests/sensors/calibration/accelerometer-data.h

src/tests/sensors/calibration/magnetometer-data.h

src/tests/sensors/calibration/test-calibration-benchmark.cpp

src/tests/sensors/calibration/test-calibration-stats.cpp

src/tests/sensors/calibration/test-calibration.cpp

src/tests/sensors/test-bme280.cpp

src/tests/sensors/test-bmx160-with-correction.cpp

src/tests/sensors/test-bmx160.cpp

src/tests/sensors/test-l3gd20-fifo.cpp

src/tests/sensors/test-l3gd20.cpp

src/tests/sensors/test-lis3dsh.cpp

src/tests/sensors/test-lis3mdl.cpp

src/tests/sensors/test-max6675.cpp

src/tests/sensors/test-mpu9250.cpp

src/tests/sensors/test-ms5803.cpp