wip: model test updates

[kirstybayliss]

This PR includes:

• updates to the descriptions of completeness norms and optimise criteria
• source_tests updates to work with point sources and to run for a whole folder
• updates on homogenisation (cat) and sub documentation
• added warnings to workflow when small catalogues are used
• adding a required sourceConverter object when merging fault and point sources
• passing on correct source names when removing fault buffers from multipoint sources
• passing sigma values from weichert_analysis to the toml file outputs when making sources
• some general tidying

wip because I apparently tried to add the option to set binwidths in the completeness fitting but I did not implement this properly, and in fact implementing this change requires some more substantial changes to the norm calculations. This only affects the optimise norm option, and only if you try to use this branch (previous version is fine, it just doesn't let you choose the binwidth). This is (at least partly) why this is currently failing.