Improve message about credit limit

To help the users deciding if they allow to overrule the credit limit, it is useful to know the exceeding amount.
Also when the credit limit of a dunning is reached, we display the dunning record name but it is just the id. So it is better to display the level name and the line name. But the line name is only the account name which is not very useful, so we could display the amount and the account code (to be short).