analyzer and service status

[Kenblair1226]

Via prometheus exporters, export running status of all services, and insert a node module in API server to export analyzers status. Prometheus will scrape every 15 seconds. When user GET /status, a json format report will be returned.

Note:

1. minio needs to be upgraded to minio:RELEASE.2018-05-11T00-29-24Z for native prometheus support
2. changed nats base docker image to bash for shell script

TODO:

• cpu and memory metrics are inside node target, need to figure out which metrics to export
• analyer status is currently got from API server. Per JiaKuan's advise, should get from AnalyzerManager
• mongodb exporter is currently using a prebuilt version, should change to runtime build