Add content-block (sir-trevor block class) to all custom blocks and add top/bottom margin to it.
Merge pull request #620 from sul-dlss/vertical-spacing

Add content-block (sir-trevor block class) to all custom blocks and add top/bottom margin to it.
remove unused Gemfile.extra file
Update Spotlight to use Blacklight 5.4 and the new if/unless feature for toggling fields on and off
refactor search results sir-trevor widget to use a custom view type widget