Subproduct attribute with additional images for options.

Rather specific, the additional images are meant to be used when the same products may be displayed directly in the catalog and used as subproducts in a "set composer".
Subproduct attribute with additional images for options.

Rather specific, the additional images are meant to be used when the same products may be displayed directly in the catalog and used as subproducts in a "set composer".
Translation and admin registration for the subproduct + image attribute.
Merge branch 'feature/configurable-products' into develop
Fixed a typo and unneeded, conflicting inheritance.
Merge branch 'feature/configurable-products' into develop
Made the new attribute visible in selection boxes in product and list attribute forms.
Merge branch 'feature/configurable-products' into develop
Translated strings for the new attribute.
Merge branch 'feature/configurable-products' into develop