story #6128 - download through HTTP the files uploaded into SFTP area

- Allow download via HTTP
- Check permissions
- Log download

Change-Id: I449687276fdaec97404cf3703a1c501e22bf714f
Updating the proftpd install docs

Change-Id: I6ae4659e0e2b338128817ab0e33f51fd3b5c20fe
Merge commit 'refs/changes/19/2019/4' of ssh://gerrit.tuleap.net:29418/tuleap into stable

* ssh://gerrit.tuleap.net:29418/tuleap:
  Updating the proftpd install docs
  story #6128 - download through HTTP the files uploaded into SFTP area

Change-Id: Ib027d47a747504942fa53d309e7fba9842722cc9
This is Tuleap 6.10.99.59

Change-Id: Ideda22dacffa775c44110e55da2ad0090d236632