Translatable image file is not working unless you also config the image field. Config can get lost anyway.

Problem/Motivation

IF you create a content type that has a translateable image ( File Property of the image ) field and you translate that image, the image of the other language get deleted.

Steps to reproduce :

• install standard profile
• install second language
• enable content translation module
• go to admin/config/regional/content-language
• Enable custom settings for content
• Set file field of image translateable
• create a article with an image
• translate the article with a different image
• the intitial article has the image of the translation

The problem can be solved this way :

• go to the content type article
• edit the image field
• set the alt and title as translateable elements
• now the translation of the image works as expected

Proposed resolution

Fix the "content language" form so it saves properly your field settings for image fields (alt and title are translatable if the file is translatable).
Also replicate the behavior that we already have in the "content language" form when you check the file as translatable (the alt and title should be checked as translatable without a choice to change that) in the image field settings form.

Remaining tasks

1. Find the bug
2. Write tests
3. Fix it