Author: Dongsheng Cai
MDL-28646 Web service: core_course_get_contents()
1. Implement core_course_get_contents web service
2. Implement callbacks in folder, resource, page and url modules
3. Implement download script for web service
http://git.moodle.org/gw?p=moodle.git;a=commit;h=ec0d6ea2a9e5ebd1a457e51e2cf639f27ca082a8
http://github.com/moodle/moodle/commit/ec0d6ea2a9e5ebd1a457e51e2cf639f27ca082a8
+ 2.2 en [courseformatnotfound,core_error]
+ 2.2 en [cannotgetcoursecontents,core_webservice]
+ 2.2 en [enabledirectdownload,core_webservice]
+ 2.2 en [unknownoptionkey,core_webservice]