formatter: Add add_newline parameter to remove '\n' from the result

[repeatedly]

KVS or Queue like plugins don't need \n in the json formatted result.
This parameter controlls \n for such plugins.

[repeatedly]

@tagomoris Could you check this patch?

[tagomoris]

The feature looks good to me.
But it seems very common thing for all formatters.
How about to add the same parameter in csv/hash/ltsv/single_value/tsv plugins?

[repeatedly]

@tagomoris Good idea. I will add this parameter to other text formatters.

[repeatedly]

Added add_newline paramter to ltsv, hash and csv formatters. single_value has already had this parameter.

moris says tsv formatter is for out_exec plugin and current implementation is not good for other cases, e.g. don't espace \t / quote field. So I exclude tsv from this patch.
CSV with \t delimiter is better for formatter plugin usecase.

@tagomoris Could you re-check this?

[tagomoris]

LGTM.