Adding feature to export results as pyam-compatible xlsx

[danielhuppmann]

Per a discussion with Joe on Twitter, this PR adds a feature to the DB_to_Excel utility to write both the original Temoa xls results file as well as a pyam-compatible xlsx file. The PR also adds a simple Jupyter notebook to conduct some useful analysis and do some visualization of the utopia results.

Open questions:

• [ ] It's not clear to me what a useful "model" description would be and how to pass that as kwarg or read from the sqlite file - I've hard-coded "TEMOA" for now
• [ ] If I understand the current code-base correctly, multi-region models are not yet supported. So I have hard-coded region="World" for now. This should be quite straightforward to extend later.
• [ ] I did not see where units are defined, so I hard-coded each unit as "?" for now.
• [ ] The variables that are exported as pyam-compatible timeseries data are emissions and all sectors of activity and capacity - the cost-related reporting is a bit tricky and I didn't find my way around the code...

[danielhuppmann]

Just realized that this PR now has conflicting changes - if there is interest to pursue integration with pyam, I'll be happy to clean this up as part of the review... Or if there is no bandwidth to do this in the foreseeable future, should I close the PR?

[TemoaProject]

Hi Daniel -- Apologies for the delay on this. We are in the midst of a couple large changes: adding an explicit region index and reconfiguring the model so it can run myopically (in addition to perfect foresight). We've added the region index, but are still working on the myopic solve. Once complete, we'll be back in touch, and may need a little help to update the PR.