[compsupp-7678] Inner Column Style Background image is not translatable

[Kitilyes]

Using Uncode theme with WPBakery builder; the back_image attribute in the vc_column_inner shortcode is not automatically translated. This leads to the same image displaying across all languages. This Commit will register the background image for both inner (vc_column_inner) and outer columns (vc_column).

Youtrack : https://onthegosystems.myjetbrains.com/youtrack/issue/compsupp-7678

[strategio]

@Kitilyes, let's wait for #411 before applying anything because we'll have a conflict with this Uncode file.

But please read my comment for Nicolas, I would ask you the same.

[strategio]

@Kitilyes, I've merged #411, so now you have to rebase and solve conflicts, or maybe just re-create your branch from the updated master.

Sorry, you should have had the priority because your PR id is lower, but didn't imagine that you were both working on the same config.

[Kitilyes]

@strategio No problem, I created a new PR using the updated master #413 , we can close #410