Add libraries for django-elasticsearch-dsl and deploy configuration

[alexm118]

Decomposes more of the Ask-CFPB work we've been doing into smaller PRs. This builds onto #6052 which now involves deploying ES7 as part of our docker stack. We've setup a flag in our ansible configuration to determine if we should configure connections to an AWS ES Cluster, or if we should default back to our standard configuration and default to an empty connection string if there is no configured ES7 Host.

---

Additions

• Configure and include django-elasticsearch-dsl connection in base.py including working configuration with an AWS ES Cluster if provided.
• Forked elasticsearch-dsl dependency where we reference elasticsearch as elasticsearch7
• requests_4awsauth to connect with AWS ES.

How to test this PR

1. App should be able to run locally, on docker enterprise, and on a DEV server even if configuration is missing such as ES7_HOST

Checklist

• PR has an informative and human-readable title
  • PR titles are used to generate the change log in releases; good ones make that easier to scan.
  • Consider prefixing, e.g., "Mega Menu: fix layout bug", or "Docs: Update Docker installation instructions".
• Changes are limited to a single goal (no scope creep)
• Code follows the standards laid out in the CFPB development guidelines
• Future todos are captured in comments and/or tickets
• Project documentation has been updated, potentially one or more of:
  • This repo’s docs (edit the files in the /docs folder) – for basic, close-to-the-code docs on working with this repo
  • CFGOV/platform wiki on GHE – for internal CFPB developer guidance
  • CFPB/hubcap wiki on GHE – for internal CFPB design and content guidance

[cwdavies]

This is a great approach to just add libraries for elasticsearch-dsl in a separate PR instead of all the changes in the Ask ES PR

[Scotchester]

Works for me in local Docker and virtualenv setups!