Add basic implementation for OpenFlow 1.4 bundles

This is only the communication part of the bundles functionality.
The actual message pre-validation and commits are not implemented.

We also enable OF1.4 for all the tests.

Signed-off-by: Alexandru Copot <alex.mihai.c@gmail.com>
Cc: Daniel Baluta <dbaluta@ixiacom.com>
[blp@nicira.com made ofputil_decode_bundle_add() more obviously correct]
Signed-off-by: Ben Pfaff <blp@nicira.com>