Encapsulate the blacklight config

All values set on Blacklight::Engine.config are actually stored
in a class variable on Railtie::Configuration. So these pollute
that namespace.  All other railties are encapsulating their configs
onto a single entry in that scope.  This change makes Blacklight do
likewise.

This probably needs to be a major revision

app/controllers/concerns/blacklight/bookmarks.rb

@@ -15,7 +15,7 @@ module Blacklight::Bookmarks
     before_action :verify_user
 
     blacklight_config.track_search_session = false
-    blacklight_config.http_method = Blacklight::Engine.config.bookmarks_http_method
+    blacklight_config.http_method = Blacklight::Engine.config.blacklight.bookmarks_http_method
     blacklight_config.add_results_collection_tool(:clear_bookmarks_widget)
 
     blacklight_config.show.document_actions[:bookmark].if = false if blacklight_config.show.document_actions[:bookmark]

app/controllers/concerns/blacklight/catalog.rb

@@ -275,13 +275,13 @@ def validate_sms_params
   end
 
   def sms_mappings
-    Blacklight::Engine.config.sms_mappings
+    Blacklight::Engine.config.blacklight.sms_mappings
   end
 
   def validate_email_params
     if params[:to].blank?
       flash[:error] = I18n.t('blacklight.email.errors.to.blank')
-    elsif !params[:to].match(Blacklight::Engine.config.email_regexp)
+    elsif !params[:to].match(Blacklight::Engine.config.blacklight.email_regexp)
       flash[:error] = I18n.t('blacklight.email.errors.to.invalid', to: params[:to])
     end
 

lib/blacklight/engine.rb

@@ -31,7 +31,9 @@ class Engine < Rails::Engine
       end
     end
 
-    Blacklight::Engine.config.sms_mappings = {
+    bl_global_config = OpenStruct.new
+
+    bl_global_config.sms_mappings = {
       'Virgin' => 'vmobl.com',
       'AT&T' => 'txt.att.net',
       'Verizon' => 'vtext.com',
@@ -42,9 +44,14 @@ class Engine < Rails::Engine
       'Cricket' => 'mms.mycricket.com'
     }
 
-    config.bookmarks_http_method = :post
+    bl_global_config.bookmarks_http_method = :post
+
+    bl_global_config.email_regexp = defined?(Devise) ? Devise.email_regexp : /\A[^@\s]+@[^@\s]+\z/
 
-    config.email_regexp = defined?(Devise) ? Devise.email_regexp : /\A[^@\s]+@[^@\s]+\z/
+    # Anything that goes into Blacklight::Engine.config is stored as a class
+    # variable on Railtie::Configuration.  we're going to encapsulate all the
+    # Blacklight specific stuff in this single struct:
+    Blacklight::Engine.config.blacklight = bl_global_config
 
     config.action_dispatch.rescue_responses.merge!(
       "Blacklight::Exceptions::RecordNotFound" => :not_found