This patch adds better core support for copying courses.
There is now a simplified and dedicated UI for copying
courses. This can be accessed from the course context
menu or course management screens.
All backups are done asynchronously and there can be multiple
copies of a course in flight at once.
The new setting will allow to host the temporary backup files
into a specific target directory. Defaults to '$CFG->tempdir/backup'.
Calling make_backup_temp_directory() checks that the required sub-directory
will be properly created under the new target directory.
Matt Porritt