bugfix for npksum + ocg
np_regression now uses hashes for gradients (lc)
added (temporary) option old.reg to npreg, eg: npreg(bw, old.reg = TRUE, gradients = TRUE) - it uses the old regression routine, to enable simple comparisons between old and new code
new regression gradients now include unordered / ordered categorical differences
shifted the hashing in the regression function around to economize space