Add `backend` and `version` to `/status`

[gaurav]

As per NCATSTranslator/NodeNormalization#377, I am proposing that the two NodeNorms add two new values to the /status endpoint.

• backend: either elasticsearch or redis. New backends can be added as needed.
• version: the version of the NodeNorm frontend. This SHOULD be the same as the OpenAPI version (https://nodenorm-es.ci.transltr.io/webapp/openapi.json) so that a tool that reads the latter isn't confused. It SHOULD use semantic versioning to indicate whether a new version breaks the previous API, makes significant changes that need to be understood, or is a small change without any API changes.

In addition, this would require:

• NodeNorm ES should restart its versioning so that it is not identical to NodeNorm Redis, i.e. produce a v1.0.0 release and then use semantic versioning to increment it when breaking changes occur.