Make helpers follow conventions

[andysellick]

According to the helpers conventions we're not following the helpers conventions. Specifically:

• some applications are using presenters when they shouldn't (finder-frontend, government-frontend and smart-answers all use shared_helper.rb, for example)
• not all helpers are named (component)_helper.rb (consequence is they are not detected by the auditing)

Unfortunately to correct this would involve a number of breaking changes and it's not actually causing huge problems right now. Maybe this needs to begin with a discussion about these conventions, why they exist and how we should handle them from now on.