Bug 527: fixed augment deserialization from xml.

Refactored deserialization process to work with augment target node InstanceIdentifier.
Codec for augmentation binded to augment target node InstanceIdentifier.
Added method isAcceptable to AugmentationCodec.
Added new interface AugmentableCodec.
Updated tests.

Change-Id: I8d83e21183b8dd55e197f3d0ad1efc68c962c842
Signed-off-by: Martin Vitez <mvitez@cisco.com>
Signed-off-by: Tony Tkacik <ttkacik@cisco.com>