Pyniva

- upgraded pandas version to 1.1

- upgraded python image used for building and publishing in circleci to 3.8.3
- hopefully this resolves problems publishing package with markdown format long_description

- added pyniva version as user agent header to all requests made to the API
- Updated readme and added it to long_description making it appear at
- removed all references to update/delete/create functions in pyniva. These do not work and are not exposed.

- clientside parameter checking of parameters
- handling of serverside http errors with status 400
- typical in cases where invalid arguments are passed
- added trace-id to all requests, and a message on errors which print the error from the server
in addition to the trace id and instructions on how to contact us with reference to cloudniva.no email

- fix package metadata and published package on pypi

- Added `raise_for_status` to some Requests calls. Some calls will
raise `HTTPError` instead of for example `JSONDecodeError`.
- Add a `session` parameter to methods that do HTTP requests (directly
or indirectly) so that we can do connection pooling and tracing, etc.