Add Local Binary Patterns implementation

This pull request adds 3 new descriptors:

1) MeanPatchIntensityHistogram: Simply constructs histogram of mean intensities of specified patch size
2) MeanIntensityLocalBinaryPatterns: Uses the former to construct histogram of local binary patterns
3) LocalBinaryPatterns: Calculates histogram of local binary patterns for each pixel

2) is based on http://dx.doi.org/10.1109/ICPR.1994.576366 and 3) is based on http://dx.doi.org/10.1109/TPAMI.2006.68

All three descriptors are accompanied by unit tests.