OpenCV "lux" plugin

This plugin simulates the ExteriorBrigtness property using a traditional webcamera.  It works
by taking the mean pixel intensity of the web camera image and estimating lux.  The particular
can be calibrated using the "pixelUpperBound" and "pixelLowerBound" variables.

To enable the OpenCV "lux" plugin, run cmake and enable the opencvlux_plugin option:

cmake -Dopencvlux_plugin=On ..

Currently, this plugin has been tested with OpenCV 2.4.4.

To use the OpenCV plugin, add the following to the "sources" array in /etc/ambd/config:

{
  "name" : "OpenCV LUX",
  "path" : "/usr/lib/automotive-message-broker/opencvluxplugin.so",
  "threaded" : "true",
  "pixelLowerBound" : "0",
  "pixelUpperBound" : "255",
  "fps" : "30",
  "opencl" : "false",
  "device" : "0"
}

NOTE: some features require the qtmainloop to be running.  see the main README for details.

Configuration Key Definitions:

"name"
name of plugin.  This key is not used by the plugin at this moment.

"path"
path to plugin on the filesystem.

"device"
Camera to use.  The string "0" corrisponds to /dev/video0, "1" to /dev/video1, etc.

Default: "0"

"threaded"
Compute pixel intensity in another thread.  Set to "true" or "false".  You need to use the qtmainloop in
order for this feature to function.

Default: "false"

"fps"
How many times per second to poll image data from the camera.

Default: "30"

"pixelLowerBound"
Lowest calibration value for a camera.  This is the average pixel intensity value the camera reports when
it is completely covered.

Default: "0"

"pixelUpperBound"
The highest calibration value for camera.  This is the average pixel intensity value when a very bright
light (like the sun) is being projected at the camera.

Default: "255"

"opencl" (experimental)
Use a specialized CPU/GPU device to calculate the mean pixel intensity.  This will only work if OpenCV
was compiled with OpenCL support.  To enable openCL, pass -Docl=ON to cmake.

Default: "false"

"logging"
Turn on video logging.

Default: "false"

"logfile"
File to encode video to.

Default: "/tmp/video.avi"

"codec"
Fourcc name of codec.  See http://www.fourcc.org/codecs.php

Default: "mjpg"

"ddd" (experimental)
Driver Drowsiness Detection.  For a driver facing camera, detect whether or not eyes are
open or closed.  If closed for a period of time, DriverDrowsiness will change to "true".

Default: "false"


Properties:

VideoLogging
Turn on and off video logging
Type: bool
Access: readwrite

DriverDrowsiness
True if the driver has been detected drowsy.
Type: bool
Access: readonly

OpenCL
True if OpenCL acceleration is enabled.
Type: bool
Access: readonly