change default ceph to firefly
work around ceph not liking gaps in ruleset numbers
use new create-or-move command
no replica count higher than the node count
default to store a replica per rack instead of host
count all nodes, not just head nodes
Revert "default to store a replica per rack instead of host"

This reverts commit 724b3d778df1354eabed8ea12fb8c26587a5b9af.
fix messed up indentation
get rid of hacks around default pool placement & size
migrate rack_name to node object
only count head or work nodes in get_all_nodes
Merge pull request #145 from pchandra/firefly

Change default ceph to firefly