Add demo config; update README

[bonicim]

• Fixes #50
• Adds demo config so that the demo openadr agent works out of the box with the toy vtn
• Updates README for clarity

[kefeimo]

For reproducibility

Able to reproduce the quick-start at Ubuntu 22.04 with Python 3.10. See the following desirable logs.

However, couldn't reproduce the quick-start at Ubuntu 22.04 with Python 3.8.

For future development to improve User experience

• Suggest creating an entry-point for utils/vtn.py script, so that users do not have to git clone the source code in quick-start.
  • ref: https://github.com/kefeimo/dnp3-python#validate-installation
  • ref: https://github.com/kefeimo/dnp3-python/blob/develop/setup.py#L131-L134
• As "openleadr" is a dependency of "volttron-openadr-ven", it is immediately available to the same virtual environment of volttron

[bonicim]

@kefeimo That makes total sense regarding making an entry-point for this toy vtn. I looked into how to do it using pyproject.toml under the Poetry framework; it was not as hard as I thought. In pyproject.toml, the equivalent of what you have in setup.py is the following:

packages = [ 
    { include = "openadr_ven", from = "src" },
    { include = "utils" }, 
]

[tool.poetry.scripts]
volttron-openadr-ven = "openadr_ven.agent:main"
vtn-demo = 'utils.vtn.__main__:main' 

I actually tested this out and it works! I will create a separate PR that will add this functionality.

[kefeimo]

For Ubuntu20.04 logs (connection established but didn't observe the desired message)

and in volttron.log