New port graphics/skanlite

This is the current version of skanlite, based on KDE Frameworks 5 and
shipped as part of KDE Applications. The legacy KDE4 version was moved
aside in r465503. Now add the modern version of the same application
and add it as a default part of the kdegraphics meta-port.

Reviewed by: tcberner
Differential Revision: https://reviews.freebsd.org/D15296