Resolve "Manage config and different envs"

Closes #343 (closed)

• Configure ICAT+ with environment variables.
• config files from test removed
• .env is a template. Default environment is dev. To run the tests, the environment is test.
• In your local machine, you can have a .env.prod and run npm run prod to start ICAT+ against the prod icat
• commands added: npm run prod, npm run dev, npm run local