Update Supported OS doc
As discussed in the mail list (Subject: Dropping support for Quantal), we need to update:
https://leap.se/en/docs/client#Supported.OSs
Support through debian packages:
- Ubuntu 13.10
- Ubuntu 14.04
- Debian 7?
- any other?
Support through bundle: the ones that are already listed in the doc.
(from redmine: created on 2013-12-23, closed on 2014-03-14, relates #5300 (closed))