Import the Project Testing Interface description

This text was approved by the PPB way back in OpenStack's history. There
are several things which have changed and have not been recorded in it,
and there is a new change that should be made. For now, this is verbatim
what was voted on in the past. Changes will follow to update to current
reality.

Change-Id: I9b5e0e5a52aab1d00497d2e8a75e9c9b249a27e9
Merge "Import the Project Testing Interface description"