Update NEWS file for version 0.3.1
Update NEWS file for version 0.3.1

Signed-off-by: Iustin Pop <acf83a5274f31a43af6b914614365999469c1a31@google.com>
Reviewed-by: Balazs Lecz <024c580adbe3324c61e798a30c60cf94ec02e89f@google.com>
Reviewed-by: Michael Hanselmann <68b67885ff74281219b4a4be33cc20fd45078d7c@google.com>

yiannist/ganeti,dimara/ganeti,leshchevds/ganeti,ganeti/ganeti,mbakke/ganeti,apyrgio/ganeti,apyrgio/ganeti,apyrgio/snf-ganeti,leshchevds/ganeti,andir/ganeti,leshchevds/ganeti,yiannist/ganeti,ganeti/ganeti,apyrgio/snf-ganeti,bitemyapp/ganeti,ganeti/ganeti,ganeti-github-testing/ganeti-test-1,ganeti-github-testing/ganeti-test-1,andir/ganeti,yiannist/ganeti,onponomarev/ganeti,mbakke/ganeti,andir/ganeti,grnet/snf-ganeti,mbakke/ganeti,bitemyapp/ganeti,onponomarev/ganeti,grnet/snf-ganeti,dimara/ganeti