Configurable related items

[ross]

Related items (Apps & Ideas) have a collection of types, which are currently fixed. Some of these types are ambiguous, such as ideas in that they may not have a link - and if they do it is likely to be to a blog post - another existing type.

Whilst the URL is required, and we think this should stay required, we should also allow users to change the types found in Apps & Ideas to a shortened list that suits their requirements.