This change adds an option to the `FieldSortBuilder` that allows to transform the type
of a numeric field into another. Possible values for this option are `long` that transforms
the source field into an integer and `double` that transforms the source field into a floating point.
This new option is useful for cross-index search when the sort field is mapped differently on some
indices. For instance if a field is mapped as a floating point in one index and as an integer in another
it is possible to align the type for both indices using the `numeric_type` option:
```
{
"sort": {
"field": "my_field",
"numeric_type": "double" <1>
}
}
```
<1> Ensure that values for this field are transformed to a floating point if needed.
5b73a1bc7d