Limit adding additional links to brand's owner.
app/views/additional_links/index.html.erb: Display item name indtead of id.
app/views/additional_links/show.html.erb: Display item name instead of id.
app/views/additional_links/show.html.erb: Back to item page with 'Back' link.
app/views/additional_links/new.html.erb: Back to item page with 'Back' link.
Merge branch 'additional-links'

Conflicts:
	app/controllers/additional_links_controller.rb