use soft link as device path

[turboc1208]

When I reboot my system sometimes my cameras end up on different video ports in the dev directory. In other systems I am able to go a sub directory under dev to find a link with the actual devices name. The applications are evidently able to use that link to get back to the correct device name. When I do this with mjpg-streamer, it does not work. for example in my case
/dev/input/by_id/283_webcam1_whatever actually points to /dev/video2. and
/dev/input/by_id/847_somethinelse actually points to /dev/video3.
by using the links under the by_id directory I don't have to worry about the video# changing when I reboot.