add clone() method to Layer class, add test.

git-svn-id: http://svn.openlayers.org/trunk/openlayers@879 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer.js

@@ -75,6 +75,30 @@ OpenLayers.Layer.prototype = {
         }
         this.map = null;
     },
+    
+   /**
+    * @param {String} newName
+    * @param {Hash} newOptions
+    *
+    * @returns A clone of this OpenLayers.Layer
+    * @type OpenLayers.Layer
+    */
+    clone: function (newName, newOptions) {
+
+        if (newName == null) {
+            newName = this.name;
+        }
+
+        var mergedOptions = null;
+        if ( (this.options != null) || (newOptions != null) ) {
+            // only merge options if there were or will be
+            mergedOptions = Object.extend( {}, this.options);
+            Object.extend(mergedOptions, newOptions);
+        }
+            
+        return new OpenLayers.Layer(newName, mergedOptions);
+    },
+    
 
     /**
     * @params {OpenLayers.Bounds} bound