Merge pull request #18 from aigualada/master

Changes to download 1.9.x package.
Fix fsdu alias reference to get disk usage
Merge remote-tracking branch 'origin/master'
Rename clean-data-files to clean-courses-files - fixes #17
Add ccf alias to clean_courses_files #minor
Extend show-disk-usage with multi-url option - refs BT#7549
Changes to solve issue in command clean_temp_folder deletes the archive and data/temp folder.