Demo/live demo 1

[sei-secheverria]

Created script to easily start up environment for live demo. More specifically:

• Added script that starts up backend and frontend, using sample negotiation card, and using same FS artifact store as the scenarios demo Jupyter Notebooks. This will simplify greatly starting up a live demo based on those scenarios. Addresses Define MLTE Presentation Demo Environment #546
• Also made minor improvement to docker compose config file, allowing it to switch and use different env files for frontend and backend as needed, without having to modify default env files.

[sei-aderr]

Didn't test out all of the environment variable options but, just running run_environment.sh worked for me with default settings and brought up a frontend and backend with the default negotiation card present

[sei-secheverria]

Thanks!