Activate KRunner instead of running the binary

Currently when we invoke KRunner and it is already running we will start binary, KDBusService will check if it is already registered and then call org.freedesktop.Application.Activate. Cutting the middle out should improve the time that it takes to show KRunner and make it less likely that key strokes are lost. If KRunner is not running we, can rely on dbus activiation to start KRunner. Unfortunately we cannnot call Activate with dbus-send because it doesn't support it's argument type. Instead we can just use the existing display method.