Migrate from ledermann/rails-settings to rails-settings-cached which allows global settings

with YAML-defined defaults. Add admin page for editing global settings. Add "site_description"
setting that would show as a paragraph on the frontpage

config/navigation.rb

@@ -7,5 +7,6 @@ SimpleNavigation::Configuration.run do |navigation|
     primary.item :domain_blocks, safe_join([fa_icon('lock fw'), 'Domain Blocks']), admin_domain_blocks_url
     primary.item :sidekiq, safe_join([fa_icon('diamond fw'), 'Sidekiq']), sidekiq_url
     primary.item :pghero, safe_join([fa_icon('database fw'), 'PgHero']), pghero_url
+    primary.item :settings, safe_join([fa_icon('cogs fw'), 'Site Settings']), admin_settings_url
   end
 end

config/routes.rb

@@ -58,6 +58,7 @@ Rails.application.routes.draw do
   namespace :admin do
     resources :pubsubhubbub, only: [:index]
     resources :domain_blocks, only: [:index, :create]
+    resources :settings, only: [:index, :update]
 
     resources :accounts, only: [:index, :show, :update] do
       member do

config/settings.yml

@@ -0,0 +1,23 @@
+# config/app.yml for rails-settings-cached
+defaults: &defaults
+  site_description: ''
+  site_contact_username: ''
+  site_contact_email: ''
+  notification_emails:
+    follow: false
+    reblog: false
+    favourite: false
+    mention: false
+    follow_request: true
+  interactions:
+    must_be_follower: false
+    must_be_following: false
+
+development:
+  <<: *defaults
+
+test:
+  <<: *defaults
+
+production:
+  <<: *defaults