This charm deploys a Ceph cluster.

It uses the new-style Ceph deployment as reverse-engineered from the
Chef cookbook at https://github.com/ceph/ceph-cookbooks

This charm is currently deliberately inflexible and potentially
destructive.  It is designed to deploy on exactly three machines.
Each machine will run mon and osd.

The osds use so-called "OSD hotplugging".  ceph-disk-prepare is used
to create the filesystems with a special GPT partition type.  udev is
set up to mount such filesystems and start the osd daemons as their
storage becomes visible to the system (or after "udevadm trigger").

The Chef cookbook above performs some extra steps to generate an OSD
bootstrapping key and propagate it to the other nodes in the cluster.
Since all our OSDs run on nodes that also run mon, we don't need this
and did not implement it.