Add support for LISP tunneling

LISP is an experimental layer 3 tunneling protocol. This patch adds
support for LISP tunneling. Since LISP encapsulated packets do not carry
an Ethernet header, it is removed before encapsulation, and added with
hardcoded source and destination MAC addresses after decapsulation. The
harcoded MAC chosen for this purpose is the locally administered address
02:00:00:00:00:00. Flow actions can be used to rewrite this MAC for
correct reception. As such, this patch is intended to be used for static
network configurations, or with a LISP capable controller.

Signed-off-by: Lorand Jakab <lojakab@cisco.com>