devel/kdsingleapplication: New port: Class that helps implement applications...

devel/kdsingleapplication: New port: Class that helps implement applications that follow the single-instance policy

Class that helps implement applications that follow the single-instance
policy referring to those applications that want to spawn a unique
instance for a given user session. Even when launched multiple times,
such applications will not spawn a number of separate instances.

WWW: https://github.com/KDAB/KDSingleApplication/