Bring footer_links back (3-1-stable)

[renatonitta]

I know it was removed according to #207, but I think it was a mistake.

The fact that the default layout of spree doesn't have a footer is not a reason to remove the footer_links.
If you work on a serious project using spree, you probably have to develop a new layout for it. Also, the designers of e-commerce market uses footer very often, normally to put things that includes static page links, like terms, return policy and stuff like that.

That is why I ask to bring footer_links back.

[ttibau]

+1

[raulpopadineti]

@RenatoCN if you want you can use my fork. I added the code back in. Make sure to use the master branch.