Refer to this app consistently.

We haven't had a consistent naming convention so far, so several
versions have cropped up:

  * Content Store
  * the content store
  * content-store
  * the content-store

I've rejected the two hyphenated versions in the name of plain English.
The choice of "the content store" over "Content Store" is
semi-arbitrary: I think it reflects how we tend to refer to this app,
but that may well reflect confirmation bias on my part.
Merge pull request #57 from alphagov/consistent-naming

Refer to this app consistently
Change the documentation around link types.

The previous documentation said that the keys represented the type of
the linked item (`organisations` or `topics`, for example); it's more
accurate to say that it's the type of the relationship itself.

For example, the `related` link type doesn't care about the type of the
thing it's linking to. As anotehr example, we could feasibly add `next`
or `previous` links for a series of items (multi-part guides, say), or
`up` links to a parent section.