This patchset adds developer overview documentation for providing
a high-level introduction to Deckhand, including its architecture,
modules, test utilities, Helm utilities, and other errata. This
work is based off this Drydock patchset:
https://review.openstack.org/#/c/571298/
Change-Id: Ic3382d4e04edf02a65184651d272fe9cd1db56a4
Felipe Monteiro