osd: 'osd COMMAND HOST:...'

Implement prepare, activate, create subcommands.  Create is basically
prepare+activate.

Signed-off-by: Sage Weil <sage@inktank.com>
install: rename *_ubuntu *_debian

It's about APT, not debian vs ubuntu.

Signed-off-by: Sage Weil <sage@inktank.com>
install: include bobtail, cuttlefish in stable release names

No reason not to support the new URLs now, even tho they don't exist yet.

Signed-off-by: Sage Weil <sage@inktank.com>
osd: do not make journal equal to disk when it is left off

Let ceph-disk-prepare handle the default journal logic.  Putting it in
here obscures information, and makes it confusing when you specify a
dir like so:

 ceph-deploy osd foo:/srv/mydir

would turn into

 ceph-disk-prepare /srv/mydir /srv/mydir

which is nonsense.

Signed-off-by: Sage Weil <sage@inktank.com>
discover: pull a ceph.conf from another host

This will let the user discover a remote host so that they can start
managing it.  Probably followed by 'gatherkeys'.

Signed-off-by: Sage Weil <sage@inktank.com>