Improve console log message on errors like 404

Former '404 Not found' plus weird HTML snippet is now: '404 Not Found:
 Page not found. Enabling the "bpapp" module might help!'

public/js/icinga/loader.js

@@ -500,7 +500,11 @@
                     this.icinga.ui.fixControls();
                 }
             } else if (req.status > 0) {
-                this.icinga.logger.error(req.status, errorThrown, req.responseText.slice(0, 100));
+                this.icinga.logger.error(
+                    req.status,
+                    errorThrown + ':',
+                    $(req.responseText).text().slice(0, 100)
+                );
                 this.renderContentToContainer(
                     req.responseText,
                     req.$target,