The previous create_module actions uses section number instead of
section id. This produces several bugs when sections are moved around
the course in edit mode. This issue implements a new_module action with
all related mutations and webservices. The new one uses section id
instead of section number.
- Add the new 'FEATURE_QUICKCREATE' to mod_subsection.
- Implement the 'before_activitychooserbutton_exported' hook callback that adds
an extra action_link to add subsections in a course section.
- Add a new permission class.
ferran