Tests on 400 413 max file size and test on unexpected response
Fix #8

5) better API - remove fake return response from delete and retrieve

4) better API - no return json from for example backup_list. Return python object instead.

1) better pass connection_timeout
2) remove ERROR_TYPES
3) unify API

* passwords can be read using pipe as well as from prompt
* password has to be reentered for create when prompt is used

Repair tests and linters

See merge request !4