Added demonstration of test plugins

#!/usr/bin/env python

from openflexure_microscope.camera.pi import StreamingCamera

from openflexure_stage import OpenFlexureStage

from openflexure_microscope import Microscope

from openflexure_microscope.plugins import PluginMount, load_plugin, search_plugin_dirs

import atexit

import logging, sys

logging.basicConfig(stream=sys.stderr, level=logging.DEBUG)

if __name__ == '__main__':

    microscope = Microscope(StreamingCamera(), OpenFlexureStage("/dev/ttyUSB0"))

    plugins_list = search_plugin_dirs([], include_default=True)

    for i in plugins_list:

        module = load_plugin(i)

        microscope.plugin.attach(module)

    # Check that default tets plugins have loaded

    print("RUNNING PLUGIN METHODS:")

    microscope.plugin.test1.run()

    microscope.plugin.test2.run()

    microscope.close()

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