Revert "reverted AlgorithmCore::compare to known stable version"

This reverts commit 480fa5d1b3c618d64dacfb8dea57f2311bfa803b.
Fix handling of empty output in updated compare
Fix updated compare breaking FuseDistance

GalleryCompare was improperly marked as independent, which broke the
online fusion scheme used by FuseDistance.
Better handling for comparing a gallery against itself

Don't enroll the gallery twice if enrollment is necessary.
Also, don't enroll the metadata twice to the same memgallery
Fix a case where multi-process wasn't used in compare

Still use multi-process mode for comparisons, even if we don't have to
enroll the probe set.
Additional comments on update compare function
Update README.md

Bitdeli is broken
Added dot distance
Merge branch 'master' of https://github.com/biometrics/openbr
Larger PCSO train/test sigsets
updated to latest janus
fixed janus edge cases
removed Janus use of C++11 feature. fixed #178
draft implementation of janus_compare
updated to latest janus
introduced Distance::compare(cv::Mat, cv::Mat)
changes suggested by Charles and Scott
few more tweaks
compile fix
switch to ppr_get_subject_similarity_score to support multi-signature templates