Fixes for new CHP fuel config; list biomass among fuels

[koen-vg]

Changes proposed in this Pull Request

It looks there was a mistake in the last CHP-fuel-related PR: there were still references to the "old" chp: true/false option in prepare_sector_network.py. And now that CHP-configuration is being improved, I thought it would be more user-friendly to also:

• List solid biomass as one of the fuels explicitly, and document how biomass-CHP is treated separately (w.r.t. parameters and CC)
• Put the micro_chp option under the new chp config section

What do you think, @p-glaum?

Checklist

• I tested my contribution locally and it works as intended.
• Code and workflow changes are sufficiently documented.
• Changed dependencies are added to envs/environment.yaml.
• Changes in configuration options are added in config/config.default.yaml.
• Changes in configuration options are documented in doc/configtables/*.csv.
• Sources of newly added data are documented in doc/data_sources.rst.
• A release note doc/release_notes.rst is added.

[koen-vg]

P.S. I put some additional comments in the chp config section, but if it's our strict policy to only document configuration in doc/configtables, I can remove the comments altogether. I do think the chp config is more self-documenting now (fewer surprises w.r.t. biomass), but the fact that biomass is treated differently than other fuels is not really obvious from the config only. From experience we know that far from all users easily find their way to the documentation.

[p-glaum]

Hi @koen-vg ,

thank you for your fix and improvement! I have just taken a brief look and it looks better :) Also, that we can now enable/disable the biomass CHP in the config setting for CHP is a good idea! From my point of view, we can merge it.

[p-glaum]

Looks good!