Update clause_specification_text.adoc

[chris-little]

Added example of a polygon with holes
Added text clarifying use of MultiPolygon and improved examples
Minor text edits

[awarde96]

I think this looks good and clarifies the multiPolygon, maybe to be more explicit we could add the range for the Polygon example with holes that there is only a single value in the range? Not fully needed but maybe helps people understand it is a single polygon.

{
  "type" : "Coverage",
  "domain" : {
    "type": "Domain",
    "domainType": "Polygon",
    "axes": {
      "composite": {
        "dataType": "polygon",
        "coordinates": ["x","y"],
        "values": [
          [ [ [100.0, 0.0], [101.0, 0.0], [101.0, 1.0], [100.0, 1.0], [100.0, 0.0] ]
            [ [100.3, 0.2], [100.3, 0.4], [100.5, 0.4], [100.5, 0.2], [100.3, 0.2] ]
            [ [100.7, 0.6], [100.8, 0.8], [100.9, 0.6], [100.7, 0.6] ] ]
        ]
      },
      "z": { "values": [2] },
      "t": { "values": ["2008-01-01T04:00:00Z"] }
    },
    "referencing": [...]
  },
  "parameters" : {
    "temperature": {...}
  },
  "ranges" : {
    "temperature" : {
      "type" : "NdArray",
      "dataType": "float",
      "values" : [273.15]
    }
  }
}

I would also add an explicit example of MultiPolygon where one of the Polygons has a hole.

{
  "type": "Coverage",
  "domain": {
    "type": "Domain",
    "domainType": "MultiPolygon",
    "axes": {
      "composite": {
        "dataType": "polygon",
        "coordinates": ["x", "y"],
        "values": [
          [
            [
              [40, 40],
              [20, 45],
              [45, 30],
              [40, 40]
            ]
          ],
          [
            [
              [20, 35],
              [10, 30],
              [10, 10],
              [30, 5],
              [45, 20],
              [20, 35]
            ],
            [
              [30, 20],
              [20, 15],
              [20, 25],
              [30, 20]
            ]
          ]
        ]
      },
      "z": {
        "values": [2]
      },
      "t": {
        "values": ["2008-01-01T04:00:00Z"]
      }
    },
    "referencing": [...]
  },
  "parameters": {
  },
  "ranges": {
    "temperature": {
      "type": "NdArray",
      "dataType": "float",
      "axisNames": ["composite"],
      "shape": [2],
      "values": [23.1, 24.7]
    }
  }
}