Refactor current_finder to current_format
Refactor current_finder to current_format

Previously specifying all the variations in naming and metadata was too
verbose. This commit refactors this helper to only require the singular
title and the class name.

alphagov/specialist-publisher-rebuild,alphagov/specialist-publisher-rebuild,alphagov/specialist-publisher-rebuild,alphagov/specialist-publisher-rebuild,alphagov/specialist-publisher,alphagov/specialist-publisher,alphagov/specialist-publisher