Various improvements

[EvanBldy]

Problem

• Some refactoring is needed.
• Some requirements are outdated.
• Some WrongParameterException are caught due to this commit 8bedda8#diff-0768568005dfcd555f8c6ff376c491eebe2ced13fe4b631ac29158939ef61e0dR119 so the messages are not in the response.
• It's impossible to override fps from entity data (FPS Override in Kitsu doesn't override video encoding #863).
• It's not possible to change the default locale for new persons.

Solution

• Refactoring.
• Upgrade outdated requirements.
• Fix problems with WrongParameterException.
• Allow to override fps from entity data when normalizing.
• Add new environment variable DEFAULT_LOCALE to set the default locale for new persons.