Support environment vars (#155)

* updage flag values from environment variables

* add log and removing unused constants

* removing unused code

* Docker build client

* fix indentation

* Documentation with docker command

* use docker volume

client/cmd/service.go

@@ -34,6 +34,3 @@ var (
 		Short: "manages wiretrustee service",
 	}
 )
-
-func init() {
-}