This moves the developer use case over to systemd, and updates all the
relevant docs to discuss the systemd workflow instead of screen. It
does so by defaulting USE_SCREEN=False, so will not impact people that
set it explicitly.
Change-Id: I6d664612bc2b850eb7f56852afbc841867223ab7
It turns out we never really had a document on how to work with
devstack in the devstack docs. At one point this was just cultural
knowledge passed down, but with the size of our community, we can't
rely on that any more.
Change-Id: I28f896ea507ccbba5164ebfc5415d22207f52e98