Http Server: Json formatter

The json formatter, format primitives to a json format.
It overload to_json method with the different types.

It can be used directly, to format return value as a json primitive.
it is also used by json objects to help them format themselfs

Signed-off-by: Amnon Heiman <amnon@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
Http Server: Change the OS version to work with the json formatter

The Os version handler use the json formatter to return
json formatted result

Signed-off-by: Amnon Heiman <amnon@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>