Update contributors and licence files, adding Gibus and I in it, and the content of the AGPL licence.
The PRIMARY AUTHORS are (and/or have been):
Renaud Bernard <renaud.bernard@sopinspace.com>
Raphaël Badin <raphael.badin@sopinspace.com>
Gérald Sedrati-Dinet <gsd@sopinspace.com>
Simon Descarpentries <sid@sopinspace.com>
The MUCH-APPRECIATED CONTRIBUTORS (people having submitted patches, reported bugs, added translations):
Kirill Miazine (http://km.krot.org/)
Paulo Rená da Silva Santarém <pbrss@yahoo.com.br>
Alejandro Martin Ortin <alejandromartinortin@gmail.com>