Add IPv6 Support.

With OpenVPN in Version 2.3 nativ IPv6 can be used. Introducted correct
parameter to puppet-openvpn to support this.
Add basic doc to server.pp for the usage of IPv6.
Merge pull request #3 from Akendo/feature/OpenVPN-IPv6

Feature/open vpn i pv6
implement recommendations by bettercrypto

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>
Merge pull request #4 from TelekomCloud/bettercrypto

implement recommendations by bettercrypto
update vagrantfile to vagrant 2 syntax

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>
Merge pull request #5 from TelekomCloud/vagrant2

update vagrantfile to vagrant 2 syntax
add multiple push entries in vpn conf
Merge pull request #6 from eumel8/feature/multiple_push

add multiple push entries in vpn conf
Allow to disable BetterCrypto to keep backward compatibility.
Merge pull request #8 from spielkind/feature/allow_to_disable_bettercrypto

Allow to disable BetterCrypto to keep backward compatibility.