Fix blacklight helper overrides - re closes #167

It appears that you need to inlcude the Hydra blacklight helpers which in turn include the Blacklight blacklight helpers in order to retain full hydra functionality when overriding or extending blacklight helpers.

See https://github.com/projectblacklight/blacklight/wiki/Configuring-and-Customizing-Blacklight#custom-view-helpers

Along with https://github.com/projecthydra/hydra-head/blob/master/hydra-core/app/helpers/hydra/blacklight_helper_behavior.rb

We can write tests for this or just treat it as a learning experience.