Refactor view helpers.
Refactor view helpers.

Split things out to make things clearer. This also allows us to more
easily customise how we render Sir Trevor content.

sul-dlss/sir-trevor-rails,madebymany/sir-trevor-rails,cbeer/sir-trevor-rails,represent/sir-trevor-rails,madebymany/sir-trevor-rails,sul-dlss/sir-trevor-rails,sul-dlss/sir-trevor-rails,represent/sir-trevor-rails,represent/sir-trevor-rails,jonduarte/sir-trevor-rails,cbeer/sir-trevor-rails,jonduarte/sir-trevor-rails,madebymany/sir-trevor-rails,jonduarte/sir-trevor-rails