This change allows individual SLO segments to be downloaded by adding
an extra 'part-number' query parameter to the GET request. You can
also retrieve the Content-Length of an individual segment with a HEAD
request.
Co-Authored-By: Clay Gerrard <clay.gerrard@gmail.com>
Co-Authored-By: Alistair Coles <alistairncoles@gmail.com>
Change-Id: I7af0dc9898ca35f042b52dd5db000072f2c7512e