add Ctrl S in usermgr

usermgr/widget.cpp

 	QShortcut* quit = new QShortcut(QKeySequence("Ctrl+Q"), this);
 	connect(quit, SIGNAL(activated()), qApp, SLOT(quit()));
 
+	QShortcut* save = new QShortcut(QKeySequence("Ctrl+S"), this);
+	connect(save, SIGNAL(activated()), this, SLOT(saveCurrent()));
+
 	setFixedSize(size());
     connect(ui->btnAdd, SIGNAL(clicked()), this, SLOT(addUser()));
     connect(ui->btnRemove, SIGNAL(clicked()), this, SLOT(removeCurrent()));