Aggregations: size property parsing inconsistent

[oswaldo]

In aggregations, the size property must be unquoted while in other places it can be quoted (tested in 1.0.0, 1.1.0 and 1.1.1)

The following work:

{
  "size": "1",
  "aggs": {
    "aggtest": {
      "terms": {
        "field": "somefield",
        "size": 1
      }
    }
  }
}

But this doesn't:

{
  "size": "1",
  "aggs": {
    "aggtest": {
      "terms": {
        "field": "somefield",
        "size": "1"
      }
    }
  }
}

Resulting in a 400 error ending in "Parse Failure [Unknown key for a VALUE_STRING in [aggtest]: [size].]]; }]"

This inconsistency is not mentioned in documentation and the error message is not very helpful, so I could only spot the problem after @honzakral pasted a working example on irc.

I believe at least a fix should be done so all fields behave the same, or with mandatory or with optional quotes, but no two fields with same name but different behaviour.