Clarify how to read and modify scenarios

[ryan-kipawa]

More clear guidance is required for working with scenarios (and perhaps a simplified API).

Related issues/discussions:
#52
#42

I suggest the following:

• Identify and add relevant methods required. #55
• Add a notebook example showing how to work with scenarios in the current form #54
  • How to list available scenarios and check active scenario
  • How to filter queries by a specific scenario (default use active?)
  • How to modify the right scenario when updating or inserting values (default use active?)
  • How to change the active scenario
• Explore how working with scenarios could be made easier if the above notebook is too verbose

[wuwwen]

Nodebook has been added. This issue can be closed.