Extend @JsonFormat annotation to apply to date objects as well.

[CheeseE]

Add @jsonformat annotation to dated fields, it is a fix for #699

[joelittlejohn]

We need to do something a little more sophisticated here. We shouldn't ever use yyyy-MM-dd'T'HH:mm:ss.SSS when we find "format": "date" in the schema.

We need to split these cases out and have a formatDates config option (c.f. formatDateTimes). We then need two methods on the annotator, dateField and dateTimeField (the current method needs to be renamed).