* videoio(librealsense): fix pipeline start with config
fix to apply pipeline settings by passing config to start.
* videoio(librealsense): add support get props
add support get some props.
this enables the usage of current sensors, while dropping support for
legacy devices, see:
https://github.com/IntelRealSense/librealsense#overview
Given limited resources, and that the legacy sensors where not that
great, I think we should focus on v2.
