Add ContourLineExtractor class to filter depth camera input to contour lines

Add ContourLineExtractor class to filter depth camera input to contour lines

This is a stripped-down version of HandExtractor.  I'll add back those
things I need to make it work.

The plan of attack:

I. Filter depth camera images to ContourLine objects
  A. translate base plane from camera-space to depth-space
  B. translate contourLineFactor from camera-space to depth-space
  C. accept depth camera framde
  D. filter corrected depth pixels
    1. shift values to "sea level" origin
    2. set non-submultiple values of contour index interval to 0xffffU
  E. trace non-0xffffU pixels to form ContourLine objects
II. Filter ContourLine objects to ContourLabel objects
  A. filter out too short ContourLine objects (i.e. not enough pixels)
  B. identify locations on ContourLine objects for ContourLabel objects
    1. try 5, 3, or 1 label per ContourLine object
  C. create ContourLabel objects
III. Add ContourLabel objects' vertices to image space
IV. Adapt vertices in vertex shader
  A. adjust for label spacing and orientation

Signed-off-by: Sean Robinson <sean.robinson@scottsdalecc.edu>