MaxOSX: settings fixes (#2371)

- Launch-At-Startup implementation for mac
- Remove "Window" tab in settings

Signed-off-by: Jonas Schnelli <jonas.schnelli@include7.ch>

src/qt/optionsdialog.cpp

@@ -45,7 +45,8 @@ OptionsDialog::OptionsDialog(QWidget *parent) :
 
     /* Window elements init */
 #ifdef Q_OS_MAC
-    ui->tabWindow->setVisible(false);
+    /* remove Window tab on Mac */
+    ui->tabWidget->removeTab(ui->tabWidget->indexOf(ui->tabWindow));
 #endif
 
     /* Display elements init */