Update Jackson and Gson dependencies

[badgerwithagun]

I've been running with these for some time.

[Flemingjp]

Looking at the change logs there seems to be no glaring issues with updating these. Just a few notes for future reference.

Jackson 2.9 Change Log
As per databind#219 java.sql.Date will finally use same "timestamp-or-String" determination as java.util.Date and java.util.Calendar. This means that with vanilla, unchanged settings, values will be serialized as numeric timestamps. Note that the default String serialization will still default to java.sql.Date.String(), and not to default formatting java.util.Date uses.