added piwikHelper.log and piwikHelper.error as cross-browser wrapper around console.log etc

plugins/Dashboard/templates/dashboardWidget.js

@@ -40,7 +40,7 @@
         _create: function() {
 
             if(!this.options.uniqueId) {
-                console.error('widgets can\'t be created without an uniqueId');
+                piwikHelper.error('widgets can\'t be created without an uniqueId');
                 return;
             } else {
                 this.uniqueId = this.options.uniqueId;

themes/default/common.js

@@ -12,6 +12,33 @@ var piwikHelper = {
         return $('<div/>').html(value).text();
     },
 
+    /*
+     * a nice cross-browser logging function
+     */
+    log: function() {
+        try {
+            console.log.apply(console, arguments); // Firefox, Chrome
+        } catch (e) {
+            try {
+                opera.postError.apply(opera, arguments);  // Opera
+            } catch (f) {
+                alert(Array.prototype.join.call(arguments, ' ')); // MSIE
+            }
+        }
+    },
+
+    error: function() {
+        try {
+            console.error.apply(console, arguments); // Firefox, Chrome
+        } catch (e) {
+            try {
+                opera.postError.apply(opera, arguments);  // Opera
+            } catch (f) {
+                alert(Array.prototype.join.call(arguments, ' ')); // MSIE
+            }
+        }
+    },
+
     htmlEntities: function(value)
     {
         var findReplace = [[/&/g, "&amp;"], [/</g, "&lt;"], [/>/g, "&gt;"], [/"/g, "&quot;"]];