Make it easier to edit payment methods

Right now it is too difficult to edit the payment methods. In #1684252: Turn 'connect with us' and 'payment methods' blocks into menus so that they can be easily edited. the payment methods was changed to a menu. However, it is way too hard to add new payment methods. I am from Denmark so I just wanted to add "Dankort". First I had to add the menu link (easy). Then I had to create a subtheme of Commerce Kickstart Theme to add my own css. Then I had to find the icons and add them to my theme. After that I had to write some css to substitute the link for an icon instead. Then I had to debug why my newly created payment method in the menu did not have any class, which I could use in my css.

It would seem much easier just to have a block, where the editor is allowed to put in images :)