- use vue components `Content` and `AppContent` with it's respective styling
to be independent from server styling
- use OCP\IInitialStateService and @nextcloud/initial-state to transmit the serverData
instead of using a hidden span element and jsonEncode/Decode
this is needed to use the `Content` component, so the vue instance can be mounted to
#content directly (otherwise server styling for #content interfers with the vue styling)
- also improves some general styling (mostly widths and margins/paddings)
Signed-off-by: Jonas Sulzer <jonas@violoncello.ch>