Debian package + repository

[daniele-athome]

Build a package for the Kontalk Tigase server and host nightly snapshots on our server. Things to be addressed:

• [x] fix dependency conflicts (there are multiple versions of some libs in jars)
• [ ] systemd script
• [ ] create dedicated system user
• [ ] startup script should use system-wide dependencies
• [ ] configuration questions before installation for: GPG key, X.509 certificate, listening ports, database (db-config integration?)