This captures some discussion over the scoping of variable names
during some recent role development. It tries to provide some
guidelines to prefixing of global variable names in roles and
"module-like" roles.
Since "deprecation.rst" is now holding a few different things, it
makes more sense as "policy.rst".
Reorganise to be nested in one more level, and add a contents section
to help find sections easier.
Change-Id: I0d551eefd33744ffa23418d0780769a7e52fe9cf
c9b4b01187