Simplified Store Interface (#545)

This PR simplifies Store and FileStore
by keeping just the Get and Save account methods.

The AccountManager operates mostly around
a single account, so it makes sense to fetch
the whole account object from the store.

management/cmd/management.go

@@ -185,8 +185,6 @@ var (
 				return err
 			}
 
-			fmt.Println("metrics ", disableMetrics)
-
 			if !disableMetrics {
 				ctx, cancel := context.WithCancel(context.Background())
 				defer cancel()