Added TypeModel model for galleries
Added basi Added basic backend module to manage galleries
Moved existing gallery classes to model class
Fix standard gallery to work like a real model

We need to fix gallery implementation, currently standard is always used
Deleted gallery factory and fixed labels
Moved gallery configuration to tl_iso_gallery DCA
Changed label for standard gallery
Controller::getImage has been moved to Image::get()
The default image size is "main"
Fixed legends for tl_iso_gallery table
Fix flag sorting of gallery backend
Select gallery config in the product type
Fixed label for blank option
Merge branch 'feature/gallery-model' into develop