Implemented IKEv2 initiator features:

Implemented IKEv2 initiator features:
- IKE_SA_INIT and IKE_AUTH initial exchanges
- Delete IKA SA
- Rekey and delete Child SA
- Child SAs lifetime policy

To set up one VPP instance as the initiator use the following CLI commands (or API equivalents):

ikev2 profile set <id> responder <interface> <addr>
ikev2 profile set <id> ike-crypto-alg <crypto alg> <key size> ike-integ-alg <integ alg> ike-dh <dh type>
ikev2 profile set <id> esp-crypto-alg <crypto alg> <key size> esp-integ-alg <integ alg> esp-dh <dh type>
ikev2 profile set <id> sa-lifetime <seconds> <jitter> <handover> <max bytes>

and finally
ikev2 initiate sa-init <profile id> to initiate the IKE_SA_INIT exchange

Child SA re-keying process:
1. Child SA expires
2. A new Child SA is created using the Child SA rekey exchange
3. For a set time both SAs are alive
4. After the set time interval expires old SA is deleted

Any additional settings will not be carried over (i.e. settings of the ipsec<x> interface associated with the Child SA)

CLI API additions:
ikev2 profile set <id> responder <interface> <addr>
ikev2 profile set <id> ike-crypto-alg <crypto alg> <key size> ike-integ-alg <integ alg> ike-dh <dh type>
ikev2 profile set <id> esp-crypto-alg <crypto alg> <key size> esp-integ-alg <integ alg> esp-dh <dh type>
ikev2 profile set <id> sa-lifetime <seconds> <jitter> <handover> <max bytes>
ikev2 initiate sa-init <profile id>
ikev2 initiate del-child-sa <child sa ispi>
ikev2 initiate del-sa <sa ispi>
ikev2 initiate rekey-child-sa <profile id> <child sa ispi>

Sample configurations:

Responder:
ikev2 profile add pr1
ikev2 profile set pr1 auth shared-key-mic string Vpp123
ikev2 profile set pr1 id local  fqdn vpp.home.responder
ikev2 profile set pr1 id remote fqdn vpp.home.initiator
ikev2 profile set pr1 traffic-selector remote ip-range 192.168.125.0 - 192.168.125.255 port-range 0 - 65535 protocol 0
ikev2 profile set pr1 traffic-selector local ip-range 192.168.124.0 - 192.168.124.255 port-range 0 - 65535 protocol 0

Initiator:
ikev2 profile add pr1
ikev2 profile set pr1 auth shared-key-mic string Vpp123
ikev2 profile set pr1 id local  fqdn vpp.home.initiator
ikev2 profile set pr1 id remote fqdn vpp.home.responder
ikev2 profile set pr1 traffic-selector local ip-range 192.168.125.0 - 192.168.125.255 port-range 0 - 65535 protocol 0
ikev2 profile set pr1 traffic-selector remote ip-range 192.168.124.0 - 192.168.124.255 port-range 0 - 65535 protocol 0
ikev2 profile set pr1 responder TenGigabitEthernet3/0/1 192.168.40.20
ikev2 profile set pr1 ike-crypto-alg aes-cbc 192  ike-integ-alg sha1-96  ike-dh modp-2048
ikev2 profile set pr1 esp-crypto-alg aes-cbc 192  esp-integ-alg sha1-96  esp-dh ecp-256
ikev2 profile set pr1 sa-lifetime 3600 10 5 0

Change-Id: I1db9084dc787129ea61298223fb7585a6f7eaf9e
Signed-off-by: Radu Nicolau <radu.nicolau@intel.com>