* Remove guarded_addons directory and associated code, migrate existing
Files are now all kept in the same directory, and download_file() view
controls access.
This removes the code that was moving the files to the guarded_addons
directory, fallback code to deal with files not yet moved, and the
crons that ensures files were moved if needed.
* Remove old setting and obsolete test
* Add migration command
* Fix test/codestyle
* Unused imports
* Remove guarded-addons directory from git
* Tweaks and tests
* Compute ETA with full elapsed time
* Simplify command: remove Entry namedtuple, passing file/dir names instead