Add video recording in HumanLogger

[davidegorbani]

At the moment when the data of the human is recorded, the video of the cameras is not, so I open this issue in order to add the possibility of recording the cameras.

CC @lrapetti

[lrapetti]

One option we discussed was to launch the YarpRobotLoggerDevice connecting just to the camera, while the HumanLogger saves the human data. In theory we would expect the two to use the same clock. However, I am not sure if the YarpRobotLoggerDevice can be launched without an actual robot running. @GiulioRomualdi?