Big remodel of opencv-rice-ann
More fun with type conversions.
Moving DMatch up to the opencv-rice library.
Some minor formatting changes.  Squelched bug in ExtendedDescriptors which was rounding off location of keypoints.
Squelched error in extended descriptor creation.
Stripped out references to FFI.
Added covariance based matcher.
Flogging the covariance brute force matcher.
Now calculting covariance.
Adding covariance matcher and covariance ratio matcher.
Added OnlyGeometryMatcher.
Some cleanup.
Applying another early-out to the covariance matcher (it doesn't work.
Got a basic OpenMP loop parallelism working.
Fixed error in Covariance matcher.
Plumbed CovarianceIndependentRatioMatcher in with Rice.
Added a few function aliases to FeatureSet