Refactor room list in multiple sub components

Also modernize the codebase where possible (e.g use required properties,
reorder properties, fix warnings, don't use Action when not needed)

Signed-off-by: Carl Schwan <carl@carlschwan.eu>

src/qml/Dialog/ConfirmLogoutDialog.qml

@@ -20,8 +20,8 @@ QQC2.Dialog {
         }
     }
 
-    x: Math.round((parent.width - width) / 2)
-    y: Math.round((parent.height - height) / 2)
+    x: parent ? Math.round((parent.width - width) / 2) : 0
+    y: parent ? Math.round((parent.height - height) / 2) : 0
     modal: true
 
     footer: QQC2.DialogButtonBox {