Log global errors

Use the global error handler, window.onerror, to catch miscellaneous
exceptions and pipe them into the debug log.

Fixes #456

// FREEBIE

js/debugLog.js

@@ -33,5 +33,9 @@
                 }).fail(resolve);
             });
         };
+
+        window.onerror = function(message, script, line, col, error) {
+            console.log(error);
+        };
     }
 })();