Feature: Height to normal map filter.

This adds a height to normal map filter to Krita.

The filter is based on the edge detection filter, so like it, it
can do prewitt, sobol and simple, as well as have a editable kernel
radius(which controls how strong the effect of a height difference is in the
resulting normal map), and it can be used as a filter layer/mask/brush.

The most common used method is sobol with a single px radius, which is also
the default it open up on.

CCMAIL:kimageshop@kde.org
BUG:330695