Adds EntityCleanupLongevityTest
Merge branch 'fix/longevity-entity-cleanup' of github.com:aledsage/brooklyn into fix/longevity-entity-cleanup
Track child entities when unmanaging entities so onUnmanaged can be called on all (child) entities
Tidied up following PR review
Merge pull request #1042 from Nakomis/fix/longevity-entity-cleanup

Fix/longevity entity cleanup