Per-environment configs

[rsyring]

• Need to be able to specify different config for different environments
• Some type of list of used/approved environments. If you have the config for each, you can use that. But then for the devs, there's going to be different environment names (e.g. rsyring.meld). Maybe the environment name in that case is always "dev" but a different ident is used in the config for the special case of "dev" environment so that any objects created in AWS have the dev's preferred ident (e.g. rsyring.meld).
• A simple app with no config for the different environs could probably give a static list of expected environment names.
• Maybe rename "environment" in this context to "profile" to avoid overloading "environment"

[calebsyring]

Wishlist:

• support for multiple project-orgs (if I want my mu lambda to exist in multiple aws accounts/environments)
• policy_arns that are different per project-org and per dev (would need to depend on environment variables somewhat)

Ideally I could also specify which mu env/namespace to use via environment variable if that's not supported already.

[calebsyring]

Regarding terminology, I propose:

• aws_account (for aws account)
• mu_namespace (for differentiating/namespacing mu resources within accounts)

[rsyring]

Did this get resolved with #27?

[calebsyring]

I didn't close this issue because I think it's a little broader in scope and has some conveniences in mind, but #27 covers the core of this.