This change moves existing files.
It is not meant to be the final word on how the main page looks or how the
other files are organized, but it gets everything roughly into shape. If
the barbican team wants to make changes, please do those as follow-up patches.
Note this does not touch the api directory, this one needs to be
migrated to the api-ref.
This is part of the docs migration work for Pike.
Change-Id: Ibb9d971806964ac185882272514ee9563089d69d