Added webmail, refreshed wiki service

Only a few days before sphere.luon.net will be shutdown, I have added a webmail service that will access Luon mail or mail on virtual domains hosted by Luon, hosted on target.luon.net.

I have also refreshed the Luon Wiki, switching from gitit to ikiwiki. We also support hosting other ikiwikis, if needed.

Make sure our SSL certificates are valid! If not, please let us know. Due to the move it could be, though, that there is a hostname mismatch (for example *.vtilburg.net with webmail.luon.net).