Added rocOption plotting functionality
Unify BEE::writeSimmat/writeMask

Similar to the read methods, cv::mat contains type information, so there is no
particular need for separate methods for masks and similarity matrices.

Also, fix an apparent bug where .mat files read by openbr were transposed
(compared to their dimensions when writing the files).
Merge branch 'master' of https://github.com/biometrics/openbr into pairwise_compare