Updated example plugin to use new JsonPayload

from openflexure_microscope.api.utilities import parse_payload, get_from_payload

from openflexure_microscope.api.utilities import JsonPayload

from openflexure_microscope.api.v1.views import MicroscopeViewPlugin

from flask import request, Response, escape

        Assumes request will include a JSON payload.

        """

        # Get payload JSON as a dictionary

        state = parse_payload(request)

        payload = JsonPayload(request)

        # Extract a value from the JSON key 'plugin_string'. If no value is given, default to None

        new_plugin_string = get_from_payload(state, 'plugin_string', default=None)

        new_plugin_string = payload.param('plugin_string')

        if new_plugin_string:  # If not None or empty

            # Set microscope attribute to the specified string