[oldlogstashjson] simplify decoding from v0 to v1
[oldlogstashjson] simplify encoding from v1 to v0
[oldlogstashjson] implement encoding of @fields
[oldlogstashjson] exclude @version from @fields during encode
[oldlogstashjson] append newline to encoded json
[oldlogstashjson] fix broken test logic in 25dc988
Merge pull request #795 from bfritz/improve-oldlogstashjson-codec

improve oldlogstashjson codec