Extract DB interface

[moshloop]

Extract https://github.com/flanksource/canary-checker/blob/master/pkg/db/init.go into a common DB interface so that it can be called as follows form any other repo:

import commonsdb "github.com/flanksource/commons-db"

db := commonsdb.Postgres{
    ConnectionString: "",
    PublicEndpoint: "",
    PostgresVersion: "",
    PostgrestVersion: "",
}

db.MustInit()
db.Start() // start embedded db's / services if necessary
db.Stop()