Move Zuul config in-repo
Move Zuul config in-repo

This moves the Zuul project configuration into this repo rather
than project-config for easier modification of check/gate jobs.

Change-Id: I235a0584d2b0156406b2d07848d484a9148d064e

switch-ch/diskimage-builder,openstack/diskimage-builder,openstack/diskimage-builder,switch-ch/diskimage-builder