doc: update README

Signed-off-by: John Spray <jspray@redhat.com>
doc/build: update 'inktankstorage' to 'ceph'

These are parts that moved when Calamari was
open sourced.

Signed-off-by: John Spray <jspray@redhat.com>
Merge pull request #126 from ceph/wip-readme

Updates to README and git paths