doc: misc updates for release-process

Signed-off-by: Gary Lowell  <gary.lowell@inktank.com>
Reviewed-by: Ken Dreyer <ken.dreyer@inktank.com>
doc: update release-process for packages

New script to sign rpms in the repo and create the indexes, and
some description of additional packages that might need to be added.

Signed-off-by: Gary Lowell  <gary.lowell@inktank.com>
Reviewed-by: Ken Dreyer <ken.dreyer@inktank.com>
doc: fix reST formatting in release-process

Signed-off-by: Ken Dreyer <ken.dreyer@inktank.com>