docs: fill out app listing CLI docs

cli/app.go

@@ -50,7 +50,16 @@ var appRestoreCommand = &cli.Command{
 	ArgsUsage: "<service> [<backup file>]",
 }
 var appListCommand = &cli.Command{
-	Name:    "list",
+	Name:  "list",
+	Usage: "List all managed apps",
+	Description: `
+This command looks at your local file system listing of apps and servers (e.g.
+in ~/.abra/) to generate a report of all your apps.
+
+By passing the "--status/-S" flag, you can query all your servers for the
+actual live deployment status. Depending on how many servers you manage, this
+can take some time.
+	`,
 	Aliases: []string{"ls"},
 	Flags:   []cli.Flag{StatusFlag, ServerFlag, TypeFlag},
 	Action: func(c *cli.Context) error {