adjust footer for correct software name ('running e621ng' instead of website name)

app/views/static/_footer.html.erb

@@ -1,6 +1,6 @@
 <footer id="page-footer">
   <span class="left">
-    Running <%= Danbooru.config.app_name %>
+    Running <%= Danbooru.config.software_name %>
     – <%= link_to "Rules", terms_of_service_path %>
     – <%= link_to "Takedowns", takedown_static_path %>
     – <%= link_to "Privacy", privacy_policy_path %>

config/danbooru_default_config.rb

@@ -12,6 +12,10 @@ module Danbooru
       "e621"
     end
 
+    def software_name
+      "e621ng"
+    end
+
     def description
       "Find good furry art, fast"
     end