Merge pull request #971 from aledsage/feature/cassandra-aggregated-metrics

Adds more enrichers/attributes to cassandra node/cluster
Tidy impl of location.newSubLocation

- deprecate LocationCreationUtils
- use LocationSpec (e.g. in JcloudsLocation)
Add AvailabilityZoneExtension (including aws impl)
Add InterAvailabilityZoneDynamicCluster
Cassandra sample app tidy
fix name in SingleWebServerExample
Merge InterAvailabilityZoneDynamicCluster and DynamicCluster

- make DynamicCluster configurable, to do inter-availability zones