Mapping: When _all is disabled, optimize to not gather all entries

[kimchy]

All entries are not gathered if specific include_in_all mapping is set on field / object level, but, if _all is disabled completely, they are still gathered. Really, don't do that... . Here is a sample mapping when _all is disabled:

{
    "my_type" : {
        "_all" : {
            "enabled" : false
        }
    }
}

[kimchy]

Mapping: When _all is disabled, optimize to not gather all entries, closed by 4634ca5.