Sub repo for security gate, add lhinds as commiter

Sub repo for security gate, add lhinds as commiter

As discussed during the OPNFV plugtest, this patch seeks to create
a releng sub repo [1] to host the anteater code for CI gate checks
around security and licence header checks.

The patch also seeks to add lhinds (security PTL) as a committer,
so they can maintain anteater code.

[1] releng-anteater

Change-Id: Ice92e3f717f5cb0e231932017975d4568249ab52
Signed-off-by: Luke Hinds <lhinds@redhat.com>