ip: ip_print: add new API to print JSON or regular format output

ip: ip_print: add new API to print JSON or regular format output

To avoid code duplication and have a ligther impact on most of the files,
these functions were made to handle both stdout (FP context) or JSON
output. Using this api, the changes are easier to read and the code
stays as compact as possible.

includes json_writer.h in ip_common.h to make the lib/json_writer.c
functions available to the new "ip_print" api.

Signed-off-by: Julien Fortin <julien@cumulusnetworks.com>