Add JSON output to knife status command

This pull request was previously known as #1650.
Please note that :
 - The hide-healthy option is now implemented as a query instead of post filtering on the client side. It provide a huge speed up
 - StatusPresenter doesn't use highline module (as NodePresenter) so i've modified the test accordingly
This is using the correct, new-style JSON encoder.  The old, incorrect form would look like `result_list.to_json`