Refactored Ajax category tree to use the common request json response rather than a custom method. Thanks to Amardeep Singh Jhajj for the help on the jQuery modification required.
This change removes the dependency on a specific JSON library from CategoryServices.

git-svn-id: https://svn.apache.org/repos/asf/ofbiz/branches/json-integration-refactoring@1634590 13f79535-47bb-0310-9956-ffa450edef68