modified the input_uvc plugin to allow for multiple camera devices
to be pulled in at once. They're passed as a comma delimited list
of devices, e.g. /dev/video0,/dev/video1. A control port is added
which listens for commands to switch cameras. The port is specified
by the new -p option.

The is the most energy and bandwidth efficient way to use multiple
cameras, since only one is streaming at any given time while the
others are paused.