add contains() function to string library. added tests too.

git-svn-id: http://svn.openlayers.org/trunk/openlayers@859 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Util.js

@@ -561,6 +561,16 @@ String.prototype.startsWith = function(sStart){
     return (this.substr(0,sStart.length) == sStart);
 };
 
+/**
+* @param {String} str
+* 
+* @returns Whether or not this string contains with the string passed in.
+* @type Boolean
+*/
+String.prototype.contains = function(str){
+    return (this.indexOf(str) != -1);
+};
+
 /**
 * @returns A trimmed version of the string - all leading and 
 *          trailing spaces removed