working toward solution for DANG best-fit vector sign problem
provisionally correct DANG
all three DANG methods working correctly.  but no tests
DANG done
NRM_dev
clean up, start working on curvature code
partial translation of taubinSVD in curvature
add PTRMS and B_lab vector; passing all tests
gamma working, but has revealed problem with get_angle_difference().  fix it
gamma mostly working, but with a little bit of weirdness