adding some funcs for Service. still need two or three more, then Service is done (but untested).

errs.go

@@ -12,6 +12,8 @@ var (
 	ErrInvalidProperty error = errors.New("invalid variant type; cannot convert")
 	// ErrNoDbusConn gets triggered if a connection to Dbus can't be detected.
 	ErrNoDbusConn error = errors.New("no valid dbus connection")
+	// ErrMissingPaths gets triggered if one or more Dbus object paths are expected but non/not enough are received.
+	ErrMissingPaths error = errors.New("one or more Dbus object paths were expected but an insufficient amount were received")
 )
 
 /*