Adjust maximal amount of characters for push notfications / news

[dkehne]

The maximal amount of characters for the push notifcations body should be adjusted to 500 (currently 250). Beside the technical adjustment of the figure you might need to check how the app is displaying a longer push-notification, e.g. is it automatically using only the first 250 chars ands add "..." behind or do we have to cut it by ourselves?