Support binary, switch-type proximity sensors. They are are exposed over the
input subsystem, emitting the SW_FRONT_PROXIMITY event code.
Also provide simple tests, based on the tests for evdev-based accelerometers.
Fixes#363
Add 2 tests for parsing the *sampling_frequency_available sysfs attribute
and then picking the closest supported value higher then the desired 10 Hz:
1: Check whether the sampling frequency gets corrected to >= 10Hz,
integer numbers sorted low to high
2: Check whether the sampling frequency gets corrected to >= 10Hz,
double numbers sorted high to low
