Unify

This MR includes:

• Small spelling correction for bin/user_importer.py, debexpo/templates/sponsor/rfs_howto.mako and docs/writing_cronjobs.rst
• Update of the initial index for the NNTP groups (as of 2019-02-12)
• Customization for the SMTP port
• Initial creation of the pub/ dir where files are uploaded

This is the last MR regarding #5 (closed). Unify has been merged with master.