Miguel Lopez authored Jun 12, 2019 and Dmitry Kazakov committed Jun 12, 2019

Implements basic version of high pass filter for Krita. More
versions may or may not to come to Krita from GIMP versions.
However, I decided not to do grayscale version as Krita already
have de-saturation filter which takes care of that part nicely.

Differential Revision: https://phabricator.kde.org/D20475