Create core_course_get_state webservice

Create an ajax webservice to load the initial state of the current course. This is a web service needed for the new course editor of Moodle 4.0.

The web service will get the course id as param and will return a structure containing all the needed information the UI components needs to operate. This will include:

• course: edition mode (bool) and section order (array of ids) (sample code)
• section: an array with all the sections data (sample code)
• cm: an array of the course-modules data (sample code)

This information will conform the initial course state each component will receive and interact with. The state will only contain information that the user can see in the course (regardless its visibility). So, for instance, hidden sections won't be returned for students.

A sample code of that web service can be checked at this proof of concept : https://github.com/ferranrecio/moodle/blob/coursecreatetest02/course/classes/external/course_get_state.php

More information about this approach with the general architecture and how this external method will be used can be found in the section "External Interface Requirements" of the course creation document.