Facets: Script statistical facets

[kimchy]

Allow to define a script to be evaluated with statistical facets, for example:

{
    "query" : {
        "match_all" : {  }
    },
    "facets" : {
        "test" : {
            "statistical" : {
                "script" : "doc['num1'] + doc['num2']"
            },
            "global" : false
        }
    }
}

Scripts can also allow for parameters:

{
    "query" : {
        "match_all" : {  }
    },
    "facets" : {
        "test" : {
            "statistical" : {
                "script" : "(doc['num1'] + doc['num2']) * factor",
                "params" : {
                    "factor" : 2.2
                }
            },
            "global" : false
        }
    }
}

[kimchy]

Facets: Script statistical facets, closed by bb24b56.