Streamline single value with boost queries: Allow for both value and query name to specify the query value

[lukas-vlcek]

As of now the prefix query accepts the following syntax:

{
    "prefix" : { "user" :  { "prefix" : "ki", "boost" : 2.0 } }
}

It would be natural to support value attribute as well. See the following example:

{
    "prefix" : { "user" :  { "value" : "ki", "boost" : 2.0 } }
}

This should be streamlined to also term, wildcard, and span_term, to allow for both value and the query name.

[kimchy]

Streamline single value with boost queries: Allow for both value and query name to specify the query value, closed by 3406e77.