added support for n-channel (n>4) images in warpAffine/warpPerspective/remap: http://code.opencv.org/issues/4190

when true, use signed gradient for the angular histogram computation.
default to false for backward compatibility.

A define was forgotten for the codecs and there was a typo for
another.

extended MinProblemSolver::Function to 1) report the space dimensionality, 2) compute gradient if needed