Merge branch '44-rename-error-classes-to-better-represent-the-error-codes' into 'master'

Resolve "Rename error classes to better represent the error codes"

Closes #44

See merge request betzms/citydoctor2!2
1 job for 43-number-of-features-in-statistics-bar-of-pdf-report-is-wrong-for-higher-numbers in 1 minute and 50 seconds (queued for 2 seconds)