Ensure all included data maximises coverage of available census tables

[sgreenbury]

This issue is to capture an aim for the countries included in v0.2 release to aim to provide metrics that cover as many census tables as possible from the source data.

[penelopeysm]

• Every derived metric partition should be pivoted to have one column for every combination of non-geoID variables
• Column names in output parquets may have to be renamed / cleaned up in a country-specific manner
• NI and Scotland data does this already, other countries (e.g. BE, US) may need to be updated