rename test
fix test `supported-locales-are-actually-supported` and improve failing message
fix some coding standards
rename old `str` namespace alias to `string`
fixing cs
rename translation id to label and explain checkpoints
remove non-existent labels in translations
add some comments
add status 0.9.12 as first checkpoint in translations, plus current supported locales
remove non-existent label from base checkpoint and fix locale->checkpoint and supported locales
format checkpoint-0-9-12-labels in several lines
add fn labels-that-are-not-in-current-checkpoint