VideoRecordingDemo: Small improvements.

- Display class of returned image matrix, so one can see if it is
  uint8 or uint16, depending on bitdepth parameter, which is hard-
  coded to 8 by default.

- Count and display unique pixel values in image, so one can easily
  gauge in 16 bpc mode if actually more than 8 bpc resolution are
  truly achieved - ie., the net-bpc, or if precision gets somewhere
  lost.
Screen: Report 'GetBandwidthUsage' of dc1394 capture in range 0-1.

Use a normalized range of 0.0 to 1.0 for 0% to 100% for reporting
usage of bus bandwidth, instead of bus units.

-> Screen for 64-Bit Octave on Linux rebuilt and tested.
-> VideoMultiCameraCaptureDemo.m demonstrates it.