Refactor hard-coded FQDN's in CloudFormation templates

[MikeTheCanuck]

Summary

With #239, we'll need the ability to substitute a different Host value in one place in the master template for each of staging and production (and any test environments we create). Until then, I'll be chasing down all the various instances of the predictable strings in hard-to-reach places.

Impact

Impacts S5.

Tasks

• Decide on naming convention for staging URLs
• Instantiate DNS records for staging domains
• Create the variable, declare their values, substitute for the various Host values scattered throughout

Definition of Done

Test environments can be deployed with the new parameterized Host values.

[MikeTheCanuck]

The Host values to be managed:

• service.civicpdx.org - domain for all API containers
• 2017.civicpdx.org/ civicpdx.org - domains for the container hosting the React applications from the 2017 project season
• civicplatform.org - domain for the container hosting the React applications from the 2018 project season