* Each param is represented as a JSON object listed in the output
  array.
* The object's "value" field contains the current value, which can
  have different types -- int, float, string or boolean.
* There is no -l form with param.show -j, each object contains the
  full description.
* But "param.show -j the_param" or "param.show -j changed" may be
  used to limit the number of objects in the output.
* Each object may or may not have any of the fields "minimum",
  "maximum", "default" or "units", depending on the param.
* Params not implemented on the present platform just have
  "implemented":false along with the param name, and no other fields.
* The values of the "minimum", "maximum" and "default" fields are
  always strings.