Use Keystone's default token format if not set

Devstack was setting its own default for Keystone's token format, so
when Keystone's default token format changed then devstack needed to
be updated. With this change, devstack will only override Keystone's
token format if KEYSTONE_TOKEN_FORMAT is set explicitly. PKI setup
is assumed to be needed unless the KEYSTONE_TOKEN_FORMAT is set to
UUID.

Change-Id: Idfa78e93abd80273dadcf37007a024bb6a783a48
Move static docs into master branch

The hand-maintained static HTML docs for DevStack have been in a
GitHub gh-pages branch; move them into the master branch in
preparation for hosting them in openstack.org infrastructure.

By default tools/build_docs.sh now builds the static HTML output
into docs/html.

Change-Id: Ide5f7d980a294c7a9f8a3decaed0939f1c239934
Merge "Move static docs into master branch"
Merge "Use Keystone's default token format if not set"
Merge branch 'master' of github.com:openstack-dev/devstack