Add support for storage command and crawler output

Partially addresses issue #3 by adding a simple `magellan list devices` command to list storage devices. To close the issue, this PR still requires including storage device information in the `crawler`'s output.

Reviewed-on: towk/magellan-ng#5

internal/util/error.go

@@ -1,6 +1,8 @@
 package util
 
-import "fmt"
+import (
+	"fmt"
+)
 
 // FormatErrorList() is a wrapper function that unifies error list formatting
 // and makes printing error lists consistent.