[MobileUI] Work around some issues with the initial swipe index

[Vogtinator]

Sometimes ListView doesn't react to positionViewAtIndex even after completion. Set currentIndex to the drawer works around that.

To avoid seeing the initial state briefly, make it invisible at first.

Additionally, show the config page for the initial setup. This is obviously more user friendly at the beginning, but I wonder whether that makes it less obvious how to get out of the configuration dialog. It would be nice to use the back button, but that appears broken because of https://github.com/nspire-emus/firebird/issues/301 currently.

Needs some testing on Android and Windows at least whether this improves the situation.