Cloudsigma provider - config and constraints

Juju provider for CloudSigma.

Provider for CloudSigma (https://www.cloudsigma.com) uses CloudSigma API v2.0 (https://cloudsigma-docs.readthedocs.org/en/2.10/).

Minimal client for communicating with the CloudSigma Web API from Go program was implemented as separate library https://www.github.com/Altoros/gosigma. This library is published under AGPLv3 license.
We tried to have reasonable default values for server configuration and use them if they are not specified explicitly. Does that make sense? Or you would prefer to throw an error if required parameters like CPU power are not set?