Add validation to Views about gaffer

[p013570]

Migration Steps

Views no longer require properties or identifiers to be provided. Instead they just require transient properties (along with filterFunctions and transformFunctions).

Views will now be validated before an operation is executed to ensure it is valid against the graph schema.

So a valid view now looks like this:

"view": {
  "entities": {
    "summaryGroup": {
      "transientProperties": {
        "average": "java.lang.Float"
      },
      "filterFunctions": [
        {
          "function": {
            "class": "gaffer.function.simple.filter.IsMoreThan",
            "value": 5
          },
          "selection": [
            {
              "key": "count"
            }
          ]
        }
      ],
      "transformFunctions": [
        {
          "function": {
            "class": "gaffer.example.function.transform.Average"
          },
          "selection": [
            {
              "key": "count"
            },
            {
              "key": "sum"
            }
          ],
          "projection": [
            {
              "key": "average"
            }
          ]
        }
      ]
    }
  }
}

this would only be valid as long as the corresponding schema defines properties "count" and "sum"

[a09631]

Merged into develop.