Notification of string changes

Author: ferranrecio
MDL-80191 backup: delegate section backup and restore
This commit adds all the logic to allow delegate sections backup and
restore. The backup and restore process is quite complex and it is not
designed to have task hierarchy. To solve the subsection problem, the
backup/restore planners do not include delegated sections at a course
level, but they are included when the activity with delegated section is
processed.

To allow restoing, the activity is responsible to store the
component/itemid mapping in the backup_structure_dbops. This way, when
the delegated section is restored (delegated sections are always
processed right after the parent activity) it can use the itemid
mapping.


http://git.moodle.org/gw?p=moodle.git;a=commit;h=b4f03323886b59b32580aeb416654d742ca25eef
http://github.com/moodle/moodle/commit/b4f03323886b59b32580aeb416654d742ca25eef

+ 4.5 en [error_delegate_section_not_found,core_backup]