Add new IKEv2 parameters

[bauerj]

The current IKEv2 implementation in contrib is working fine but lacking some constants.

I have added some IKEv2 attributes for algorithms that are unkown in this implementation. All algorithms are registered with IANA so they should probably be here. I presume the IDs have been assigned after this was written which is why it's missing.

I tried to follow the current naming convention where it differs from the IANA assigned names.