Add description to "exclude from translation"

Additionally to the description, we should try to have it shown below the regular translate checkbox and use states to only make it visible then.

Let's make this. :)

I think we can instead specifically explain what it does in TMGMT, something like "This field will no longer be exported and translated by Translation Management Tool but can still be translated manually.".

Also, screenshot :)

Ha! indeed, thank you. :)

If the bundle is not translatable then the translatable checkbox is disabled and checked and our checbox is visible too.. lets just hide it then in that case:

OK, hope this works. :)

BTW it seems that hooks of content translation go after the ones in tmgmt so I copied the logic for making the translatable checkbox disabled.

Committed, thanks.