HighAvailability demo: add availability zone config
Wide-area cassandra: set default location in main
SshJcloudMachineLocation.region: fix setting name

- if no region-scoped name, then look up-one and use the provider's name
- e.g. Rackspace VMs have no "region"; they will have a zone such as 
  "LON" and a provider name such as "rackspace-cloudservers-uk"
Add CassandraNode.LIVE_NODE_COUNT
CassandraNode's ip choice: customise for rackspace

- Choice of when to use public/private IPs is cloud-provider specific,
  depending on whether it has two separate NICs etc.
- TODO Have hard-coded that for rackspace (yuck) just now.
Make CassandraCluster.DELAY_BEFORE_ADVERTISING_CLUSTER configurable
CassandraCluster/Fabric: setting & updating seeds