Better startup status checks

[pferrel]

harness start and harness status print various settings but do no real status checks for the services that are required.

Status for Mongo. Elasticsearch, and anything the engine's want to provide should be listed.

These will be several different types:

• Harness Required services, Mongo, Auth-server (optional)
• Harness Toolbox services, Elasticsearch
• Engine services such as VW for the CB. We need an Engine API that probes these