Redirect old HMDA API documentation URLs to the new docs

[niqjohnson]

Do not merge until Sept. 25

The old HMDA API is being decommissioned, so we need to redirect the old docs to the new docs.

Additions

• In what looks like an oversight, there was no page at the root, so http://cfpb.github.io/api/ currently shows an unstyled version of the repo's README. I added a simple index.html which just redirects to the CCDB API's landing page, since those docs will be the only thing left here once the HMDA API docs are removed.

Removals

• All of the documentation content in the markdown files
• All of the console static files

Changes

• All HMDA API github.io documentation pages now redirect to the new documentation at https://cfpb.github.io/hmda-platform/#data-browser-api. I did that redirect with a <meta> element since we can't do anything server side (we did the same thing in the Design Manual when we shut that down).

Testing

1. Fire up this branch locally with bundle exec jekyll serve --watch --baseurl '/api'
2. Visit any HMDA API docs page, like /api/hmda, /api/hmda/console, or /api/hmda/queries; you should be immediately (or almost immediately) redirected to https://cfpb.github.io/hmda-platform/#data-browser-api
3. Visit the API landing page, /api; you should be redirected to the CCDB API docs landing page, /api/ccdb
4. Visit some CCDB API documentation pages (anything under /api/ccdb/) to verify that they are unchanged and still match what's live right now.