Get the state of the specified persistent parameter. The state will be
returned in the supplied callback. The state is represented as a
namedtuple with members: `is_stored`, `default_value` and
`stored_value`. The state is `None` if the parameter is not persistent
or if something goes wrong.

| Member            | Description                                     |
| ----------------- | ----------------------------------------------- |
| `is_stored`       | `True` if the value is stored to eeprom         |
| `default_value`   | The default value supplied by the firmware      |
| `stored_value`    | Value stored in eeprom, None if `not is_stored` |

Store the current value of the specified persistent parameter to
eeprom. The supplied callback will be called with `True` as an
argument on success, and with `False` as an argument on failure.

Clear the current value of the specified persistent parameter from
eeprom. The supplied callback will be called with `True` as an
argument on success, and with `False` as an argument on failure.

So that the same callback can multiplex for a lot of parameters.

When doing persitent param operations, check that the parameter is
persistent. Otherwise throw exception.

To make sure they get treated in the same queue and do not
race against each other.