Feature/support settings per device (#640)

* Optionally prevent deletion and mutation of "MutableListSetting" items

* Save server metadata per device

This makes it possible to e.g. have different settings on a desktop and a smartphone.

src/components/navbar/ReaderNavBar.tsx

@@ -184,6 +184,7 @@ export function ReaderNavBar(props: IProps) {
 
         // main container and root div need to change styles...
         rootEl.style.display = 'flex';
+        rootEl.style.flexDirection = 'column';
         mainContainer.style.display = 'none';
 
         return () => {