changed gradient to imggrad, edited edgecon

renamed gradient to avoid issue with built in gradient function. edgecon
now calls in equi directions (in degrees, perpendicular to gradient
direction) and has an allowable range for the angle of lines added based
on equi.

still havine some issues with edgecon closing shapes. need to think
about spur, skel, diag, etc and their effects as well as rng angles.