Queries for residential heating technology chart

[KoenvanB]

This PR adds queries for the residential heating technology chart. See PR #4216 in ETModel. The PR includes:

• queries to calculate the number of residences for each space heating technology, ordered by build year;
• queries to calculate the total number of residences for a build year class (currently unused)

Discussion

• Is the systematic naming of the queries in line with existing queries? E.g. is a distinction required between 'households' and 'residences'?
• Should the number_of_residences_<build_period> queries need to be based on the build year node groups?

[mabijkerk]

In general, the queries are looking good. Nice work @KoenvanB!

I think it would be very useful to write a short mechanical turk spec for this. For example, one test to check if all the queries per technology sum to the number of units of that technology and one test to check if all the queries in the chart sum to the total number of residents.

Is the systematic naming of the queries in line with existing queries? E.g. is a distinction required between 'households' and 'residences'?

I might have a small preference in this case to write all queries like this: number_of_houses_{YEAR}_{HEATING_TECHNOLOGY}. This reflects the node names which are e.g., terraced_houses_before_1945. I'm not exactly sure nor happy with the difference between residences and houses. Maybe @Charlottevm can weigh in on this?

[KoenvanB]

@mabijkerk I have

• deleted redundant empty lines in all files;
• used the node groups to calculate the number of residences per build year;
• moved those queries to general;
• changed the names of all queries for the chart to refer to number_of_houses instead of households

That makes this PR ready to merge