Make Breeze Dark use same Kolourpaint icon as Breeze
For a while now, Breeze Dark icons have had a different Kolourpaint icon. I think the Breeze version looks better and has better contrast, plus it's good to use consistent icons.
Also, reduce size and format code
Reviewers: VDG, filipf, ngraham
Reviewed By: VDG, filipf, ngraham
Differential Revision: https://phabricator.kde.org/D21521