Added new function, import_backup_file_silently
Changed everything that prints stuff to check for a constant first.
Backup_flush checks a different constant, this is so that output can still
get flushed to the browser when necessary but not print <li>s everywhere.
Please test this!
This patch allows the much requested selection of individual instances of modules within a course to backup and restore.
It needs A LOT of testing and probably some prettyifying too.
Complete refactoring of the system that was really awful (my fault!).
Now everything is in its place and working like a charm, making things really
easier to be implemented and amplied. Bug 3678
(http://moodle.org/bugs/bug.php?op=show&bugid=3678)
(http://moodle.org/mod/forum/discuss.php?d=26530)
Note: Everything is merged from stable but the quiz module because it has
other changes not merged for now. I've skyped a message to Gustav about it.
Merged from MOODLE_15_STABLE