IKEv1 and IKEv2 support

[dr1ss]

Would be great if we could check these protocols..
They might be a little tricky because there is so many ways to configure them. Several authentication mechanisms like certificates, psk (shared key) and login/pass (eap, xauth..). The good thing is that they work similarly.
IKEv2 is becoming the new standard in the VPN world and it would be a great addition for this plugin.

[danfruehauf]

@dr1ss Thanks for the feedback. At the time I intended to add support for those, but lack of time prevented me from doing it eventually.

Feel free to hack on it and add support, you will probably have better knowledge than me in those protocols...