Cleanup ofp nicira extension

Cleanup ofp nicira extension

Fix warnings coming from uint type widening and clean up builder
usage.

Also optimize MatchUtil.ipv4ToLong() by using IetfInetUtil, since
which is the most efficient way of during that conversion. This
leads to a cleanup of MatchUtil, which is taught to operate on Uint32
instead.

Change-Id: I6219f47d4dc06b046b1fce5c7acd699edd96d3ad
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>