Currency-cloud

- Adds get payment level fees api
- Adds get quote payment fee api

- Adds bank details endpoint

* Add Payment Delivery Date endpoint
* Add Account Payment Charges Settings endpoint
* Remove deprecated VAN endpoints (**breaking change**)
* Update dependencies
* Minor updates

- Bugfix for *str* method in api error (35)

* Remove deprecated functions
* Update dependencies
* Minor cosmetic changes

* Add new Sender and Reporting endpoints
* Add Conversion Cancel, Conversion Split and Conversion Date Change
* Add Payment Submission, Payment Confirmation and Payment Authorization
* Fix minor bugs
* Deprecate obsolete endpoints
* Add support for Python 3.7