Hardcode the sliding sync proxy. (#502)

* Add support for migrating between versions.
* Rename InfoPlistReader property.
* Bump SDK version.

ElementX/Sources/Screens/Authentication/LoginScreen/View/LoginScreen.swift

@@ -64,6 +64,7 @@ struct LoginScreen: View {
         LoginServerInfoSection(address: context.viewState.homeserver.address) {
             context.send(viewAction: .selectServer)
         }
+        .disabled(true) // The button is disabled for this demo.
     }
     
     /// The form with text fields for username and password, along with a submit button.