Executed files are not inputs
Accepts files in /tmp as outputs

There is already a check that the file exists at the end of the run.

This is useful at least for our own tests.
Adds 'chroot upload' test
Factors FileUploader
Adds 'chroot download' test
Don't fail on C coverage reports
Factors FileDownloader
Merge branch 'factor-upload-download' into 'master'