Don't overwrite pre-existing Partition metadata in galleries
Add sigsets for the LFW test protocol
Preliminary framework for pairwise comparisons
Refactor BEE::readMask and readSimmat to a common readMat function

Since .mtx files include a matrix type in their header, we don't really need
separate functions to read similarity matrices and masks.

This drops special case support for creating identity matrices via readSimmat
and readMask (since in that case, there is no actual header to read to get a
matrix type).
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
Handle column -> row major in matFormat correctly

We do need to do a transpose, but the inital matrix should have columns and
rows reversed, so that the matrix side remains correct.
Consolidate mask/mtx formats
Merge pull request #131 from biometrics/pairwise_compare

Add support for doing eval in terms of a series of pairwise comparisons