Juntagrico-billing

* fix path to datatables static (juntagrico)

- another digit rounding fix
- businessyear is now editable in admin UI

- Bugfix with rounding of decimal digits. Prevents error displaying QR-code for certain amounts.

* Fixed a bug that prevented displaying an invoice when the open amount was negative (overpaid)

App reference in settings.py
In your `settings.py` file you need to move `juntagrico_billing` up, so it appears before `juntagrico`.

INSTALLED_APPS = (
'juntagrico_billing',
'juntagrico',
...
)


Use new URL path pattern
Update your `urls.py` to use the `path` function instead of `re_path`:

urlpatterns = [
...
path('', include('juntagrico_billing.urls')),
]

* Show a swiss QR payslip for "normal" IBAN accounts too
* Bugfix on CAMT payment files import for QR-IBAN payment processing
* Several small bugfixes and some cleanup