Betterrev code and documentation update

[Martijn Verburg]

Hi all,

FYI - the Betterrev project has moved to play 2.2.1 (and several other
library bumps) - we've also overhauled the documentation and wiki starting
at: https://bitbucket.org/adoptopenjdk/betterrev/overview

In particular there is a Grand Plan -
https://bitbucket.org/adoptopenjdk/betterrev/wiki/Test%20and%20CI

and Workflow - https://bitbucket.org/adoptopenjdk/betterrev/wiki/Work%20Flow

Section that's good to get an overview of the project.

Cheers,
Martijn