create client configs with stronger encryption

Signed-off-by: shammash <shammash@autistici.org>

autovpn/vpn_app.py

@@ -45,6 +45,10 @@ key %(cn)s.key
 crl-verify crl.pem
 ns-cert-type server
 tls-auth tlsauth.key 1
+auth SHA512
+cipher AES-256-CBC
+tls-version-min 1.2 or-highest
+tls-cipher TLS-DHE-RSA-WITH-AES-256-GCM-SHA384
 '''
 
 TBLK_PLIST_TEMPLATE = '''<?xml version="1.0" encoding="UTF-8"?>