This covers all the features, improvements, and fixes that went into

Review Board 4.0, along with installation instructions, upgrade notes,

and comaptibility changes.
It's a big release with a lot to cover. The focus on the release notes

was to discuss the installation-related topics first, and to follow that

up with all the new feature changes, followed by bug fixes.

Built the docs. Checked for build errors, link errors, and spelling

errors.