GridHelper: Simplify .clone()

src/helpers/GridHelper.js

@@ -72,9 +72,7 @@ GridHelper.prototype = Object.assign( Object.create( LineSegments.prototype ), {
 
 	clone: function () {
 
-		var parameters = this.parameters;
-
-		return new this.constructor( parameters.size, parameters.divisions, parameters.color1, parameters.color2 );
+		return new this.constructor().copy( this );
 
 	}