Removing support for SSLv3

It's only IE6 on XP left which can't support TLS v1.x. So at this point it's time to make the move. For reference, at the time of writing, this configuration [gives an A](https://www.ssllabs.com/ssltest/analyze.html?d=apptest10.app.intelliplan.eu&hideResults=on) even with SSLv3 turned on. Furthermore, we can't turn off TLSv1 at this point, because there are many clients out there which can't switch to TLSv1.1 or TLSv1.2, so we can't realistically mitigate BEAST server-side, other than what's been done with the cipher prioritisation above (TLSv1.2 ciphers on top). [more on BEAST](https://community.qualys.com/blogs/securitylabs/2013/09/10/is-beast-still-a-threat)