Removes bottom margin from last selected link
Merge pull request #439 from moneyadviceservice/selected-nav-fix

Removes bottom margin from last selected link
Just delegate to object rather than defining a method to do so
Use provided helper rather than decorating associated entities manually
Create domain object to represent a collecion of related content items
Allow a list of categories to have their contents restricted to a specified set of items
Remove domain logic from decorator and use domain object to generate related content links