Add the doc build tools

tools/build_docs.sh generates the devstack.org website from the static
pages and generated pages created by running shocco against a DevStack
checkout.

Note that while this is the complete auto page generation of the
devstack.org site it does not yet push the content back to GitHub.
The -p options works, this is a permissions/repo issue.

Change-Id: I61dc3d56e4a4832a9ddd1904dd8af65c15a17e50
Fix typos and thinkos in docs

Change-Id: If2da63e62a14894e498b4163b5052d9b2b2069ed
Merge branch 'docs-shocco' into dt-test
Merge branch 'doc-fixes' into dt-test