Add support for background color app setting

tailbone/templates/base.mako

@@ -11,6 +11,12 @@
     ${base_meta.favicon()}
     ${self.header_core()}
 
+    % if background_color:
+        <style type="text/css">
+          body { background-color: ${background_color}; }
+        </style>
+    % endif
+
     % if not request.rattail_config.production():
         <style type="text/css">
           body { background-image: url(${request.static_url('tailbone:static/img/testing.png')}); }