Refine Mixin Integration with Lambdas

[freeformflow]

@dyoder, I'd like your thoughts on this in particular.

We recognize the power of mixins to add configuration and services to a given deployment. We've got a start on a preprocessor framework to handle adding mixins to the CloudFormation description.

However we don't as of yet have a good way to let the Lambda handlers know about the mixin configuration. A perfect example of this is in the micro-blogging example app, there's not a good way to enter the S3 bucket name we're using for data persistence. That forces you to make code changes to that bucket name whenever you wish to deploy to a new environment.

This could be a corollary ticket to #11. It's something to consider addressing in the near term before we introduce more varied mixins.

[automatthew]

Noodling:

• the FE needs to know the URL of the HTTP API
• the Lambda handler function needs to know about the CloFo Stack
• the CloFo stack needs to know everything.