The translation of sections edited by VE are saved. They need to be restored against its source sections when translation is resumed.
 The basic algorithm is to match against the section identifiers.
 If source article changed heavily, we need to use a better algorithm to identify source sections even if it changed.
 And fallback to original source revision if source article changed beyond restoring a saved translation.
 Status message about fetching the saved translation should be shown to translator
 Status message about restoring the fetched translation should be shown to translator