Created basic elasticsearch node
Added additional sensors
Added config keys required for clustering
Added support for elastic search cluster
Fixed (and simplified) clustering, using automatic zen discovery
Updated following PR review
Convert DynamicGroupTest from groovy to java
Convert AttributeMapTest from groovy to java
Convert AttributeTest test from groovy to java
Convert GeoscalingScriptGeneratorTest from groovy to java
Convert BrooklynMetricsTest from groovy to java
bump maven-war-plugin version (old version was fine here but new version needed in downstream projects),
along with the parameter which fixes the second copy overwriting the files changed by the replacer plugin (for war plugin v 2.1+);
confirmed the resulting WAR is identical apart from the pom changes
Fix for failing ItemsInContainersGroupTest

- don’t do group.addMember if member is no longer managed
Fix NonDeploymentManagementContext.toString

- avoid StackOverflow in toString
- happened in circumstances where entity.toString called
  entity.getConfig, which called entity.getExecutionContext(), which
  threw an exception in checkInitialManagementContextReal, which
  tried to call NonDeploymentManagementContext.toString
Updated following PR review, added integration tests
Server pool entity
Adds MachineEntity class for use in server pools
Server pool tests use EmptySoftwareProcesses as the pool member spec
Update MachineEntity with attributes class from Docker
Addresses server pool review comments