Add a manual test for Unity launchers

This utility allows to test and simulate unity launchers since dbus-send cannot handle
"variant maps" (a{sv}) required by this API.

unitylaunchertest org.kde.dolphin --progress 50
unitylaunchertest org.kde.kwrite --count 3
unitylaunchertest org.kde.konsole --urgent

Differential Revision: https://phabricator.kde.org/D3821