Add AlarmDefinition information to returned Alarm json

This is so the UI doesn't have to query again to get the name
of the AlarmDefinition. Also has severity

As soon as the CLI is changed, the alarm_definition_id field will be
removed from the alarm json. The id field inside the
alarm_definition object should be used instead

The extra information is represented as an interior object in the
json and looks like:

    "alarm_definition": {
      "severity": "LOW",
      "id": "52af7345-292d-4ac8-808b-249207fe91ab",
      "links": [
        {
          "href": "http://localhost:8080/alarm-definitions/52af7345-292d-4ac8-808b-249207fe91ab",
          "rel": "self"
        }
      ],
      "name": "high cpu and load"
    }

Implemented equals and hashcode for Alarm

Remove unused parameter to Alarm constructor

Change-Id: I32f7c2c780898541acf596e5c4c2b4f14824fb76
Merge "Add AlarmDefinition information to returned Alarm json"