Add a "--dev" flag or similar way to automatically set development environment

[greglucas]

For ease of use, I think we could add a "--dev" flag to the tool for command line users. This would be much easier than having to set an IMAP_DATA_ACCESS_URL and WEBPODA_SYSTEM_ID etc. and we could handle that for them.

Idea is that --dev could set the URL and SYSTEM_ID for the user directly when that flag is passed in.

[greglucas]

Actually, I wonder if we'd want to set the SYSTEM_ID or not. Because I have a feeling we might want to use webpoda from the flight system while on our development server.