Allow to specify currency when creating a manual bank access (fix #1120)
Instead of hardcoding the currency I used a custom field from the access and each account created uses this custom field as currency value.
This would allow to reuse the manual bank in an easier way (https://community.kresus.org/t/nouvelles-fonctionnalites/253/13) with a constant currency.
If the user really needs another account in USD he can now create another manual access in USD.