remove comment from init.rb
add setting value for :disable_article_summaries
sync translations for :disable_article_summaries
don't show the summary input field if it has been disabled
don't show summaries in the article table if they're disabled
change how we check for disabled summaries
remove the summary tab, move summary to article, and check if summary should be rendered
Merge branch 'feature/add-summary-visibility-toggle' into 3.x-devel

This addresses the discussion started in GH#180 by allowing the article summaries to be
toggled off at the plugin settings level.

By default they will be left enabled, in order to maintain backwards compatibility