Add check psql connection

[mcmikius]

Need to add a connection check with PostgreSQL

The function should take the POSTGRESQL connection options and return check the connection result.

Connection options example:
hostname: "localhost", username: "username", password: "password", database: "database"
or
url: "<connection string>"

Result example:
{ "componentId": "dfd6cf2b-1b6e-4412-a0b8-f6f7797a60d2", "componentType": "datastore", "observedValue": 75, "status": "warn", "time": "2018-01-17T03:36:48Z", "output": "", "links": { "self": "http://api.example.com/dbnode/dfd6cf2b/health" } }

Also need add unit tests