Waste less space in the UI

* Adjusted layout margins

   Nested layouts lead to lots of wasted space.
 * Removed unnecessary "Close" button

   Closing the settings dialog via "x" or the close button does not make
   a difference so it can savely be removed.

src/general.cpp

@@ -6,11 +6,6 @@
 #include <QFileDialog>
 #include <QStandardPaths>
 
-void AdvSceneSwitcher::on_close_clicked()
-{
-	close();
-}
-
 void AdvSceneSwitcher::reject()
 {
 	close();