ceph-volume: add raw mode

ceph-volume: add raw mode

list, prepare, activate, create (prepare+activate) basic bluestore OSDs
on a single device.

No support (or plans to ever support) dmcrypt.

I think support for db/wal could be added later without much trouble.

For now, we require --no-systemd and --bluestore flags because we haven't
implemented support for anything else but suspect we will in the future,
and would like to ensure users are being explicit about what they're
asking for.

Signed-off-by: Sage Weil <sage@redhat.com>
(cherry picked from commit 1e9de77add67fa94204c450c52d22fc3a33d7b22)