Modify helper functions files' permissions.
Fix typo in PSD projection function.
Bug fix in SOP helper function. There was no variable n. Add also assert for safety
Get impostors using exact method.
Gradient update with helper diffimp to compute the difference of
triplets representing impostors.
Update lmnn accordingly and move checks on x and y from getGenNN to
lmnn.
Fix typo and simple test for lmnn