Add capability to take timed pictures with webcams.py
Work with integers when computing disparity

This is simply a speed maneuver. I haven't been hurting for speed yet,
but as soon as you embed the process inside a whole bunch of other
real-time computations, you'll want every millisecond - especially since
I'm really thinking about putting this on a stand-alone device in the
long run.
Reorganize `'CalibratedPair``

The method order is now more logical, before they were basically ordered
chronologically, which was annoying me while extending the class.
Merge branch '3d-display' into visualize-pc

Conflicts:
	src/cam_calib/tune_calib_pair.py
Collect depth to disparity map manually

cv2.stereoRectify was giving me woefully bad results. As much as I dislike
guessing the camera's focal length from the image width and the like, it's
likely that the cameras used with this library will always have focal length
similar to human eyes, so the assumption is reasonable.
Extract 3d computations and point cloud work to new separate classes

blockmatchers.py - My results with the OpenCV's ``StereoBM`` have been
disappointing, but I don't want to lose the work I've done with that
class. Nonetheless, my results with ``cv2.StereoSGBM`` are much better.
This has led me to abstract both ``cv2.StereoBM`` and ``cv2.StereoSGBM``
into their own wrapper classes with a common API that is simply
addressed by the ``CalibratedPair``. This moves a lot of code that was
related to block matching from ``CalibratedPair`` into the places where
it belongs.

point_cloud.py - OpenCV has a nice example of exporting a point cloud to
a PLY file for viewing in MeshLab, which is very handy. This class
exposes the same functionality without requiring the user to manually do
the bookkeeping.

tune_calib_pair.py - The new functionality has now been built into
``CalibratedPair``.
Add utility to convert images to point clouds
Divide StereoBM results by 16 to match StereoSGBM
Rework block matching tuner to be compatible with BlockMatcher classes

The ``StereoBMTuner`` is now a ``BMTuner`` that autodiscovers settable
parameters in the ``BlockMatcher`` that is passed to it.

This makes the code a little shorter and simpler. As long as the
``BlockMatcher`` the ``BMTuner`` receives fulfills the required API
requirements, the ``BMTuner`` can interact with it and creates the
appropriate toolbars needed to tune the ``BlockMatcher``.
Update UI to allow usage of new classes
Bugfix: BlockMatchers now export and import from file correctly
Remove unused function
Allow img_pair_2_ply to use both block matchers
Make StereoSGBM default block matcher

My results with the StereoBM are consistently bad, so I'm switching the default
behavior to use the StereoSGBM.