Update for RfcLanguage selection in translation

- Instead of displaying duplicate RfcLanguage names with their respective study prepended,
  we now ignore duplicates by their LanguageIx.
- Improves 7135220 and relates to #34
Removed migrate.php

- The migration to the 'new' DynamicTranslation layout based on TranslationProviders
  is long done, and no current problems with the old schema still being used are known.
Implemented the SpellingLanguagesTranslationProvider.

- Remove DynamicTranslations with Category fitting /^LanguagesTranslationProvider-.*(Short|Variety)Name$/
  - I shall clean these out once a805c8c is resumed and implemented.
- I need to add a description for ShortName in RegionLanguages
- Closes #43