Added elasticsearch7 commodity

[james-r-hmlr]

• What kind of change does this PR introduce (Bug fix, feature, docs update, ...)?
  Adds Elastic Search 7 as an optional commodity (Elastic Search 5 still exists as separate commodity)

• What is the current behavior?
  'elasticsearch7' can be added to an application's configuration.yml file to automatically spin up a Elastic Search 7 container

• What is the new behavior (if this is a feature change)?
  Existing Elastic Search 5 commodity should remain unchanged

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