Added support for dynamic commands.

Dynamic commands are user commands that can be added dynamically to
the hub by a plugin.

The example plugin (mod_example.c) adds a !example command that when
invoked send a message to the user who invoked it.

src/tools/admin.c

@@ -30,6 +30,7 @@ static int handle(struct ADC_client* client, enum ADC_client_callback_type type,
 
 		case ADC_CLIENT_PASSWORD_REQ:
 			puts("*** Requesting password.");
+			break;
 
 		case ADC_CLIENT_LOGGED_IN:
 			puts("*** Logged in.");
@@ -84,10 +85,7 @@ int main(int argc, char** argv)
 	ADC_client_set_callback(&client, handle);
 	ADC_client_connect(&client, argv[1]);
 
-	while (running)
-	{
-		net_backend_process();
-	}
+	while (running && net_backend_process()) { }
 
 	ADC_client_destroy(&client);
 	net_destroy();