Add graphviz generation and visualization

This requires graphviz to be installed on your machine. If you run the
command with sudo, it will create the files with the original user
ownership to make it easier to remove them without root.

service.go

@@ -45,6 +45,10 @@ func NewServiceType(name, state, startup string) *ServiceType {
 	}
 }
 
+func (obj *ServiceType) GetType() string {
+	return "Service"
+}
+
 // Service watcher
 func (obj *ServiceType) Watch() {
 	// obj.Name: service name