This updates the Perforce configuration docs to more clearly walk people

through the requirements, setup procedures, and options for Perforce.
Most of this involves fixing up stale links to Perforce KB articles and

reworking our content into bullet point form to better help people

follow along.
Some old content (like notes around p4python SSL support, which is a

requirement these days) have been removed.
Information on what's required for user accounts has been added, helping

people get the right type of set up ahead of time.

Built the docs. Checked for spelling errors, build errors, and bad links.