Improve rate-limiting error message in registration and code verification views.

// FREEBIE

src/Network/API/TSNetworkManager.h

@@ -1,9 +1,5 @@
 //
-//  TSNetworkManager.h
-//  TextSecureiOS
-//
-//  Created by Frederic Jacobs on 9/27/13.
-//  Copyright (c) 2013 Open Whisper Systems. All rights reserved.
+//  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
 //
 
 /**
@@ -23,11 +19,11 @@
 #import "TSUnregisterAccountRequest.h"
 #import "TSUpdateAttributesRequest.h"
 #import "TSVerifyCodeRequest.h"
-
-
 #import <AFNetworking/AFHTTPSessionManager.h>
 #import <Foundation/Foundation.h>
 
+extern NSString *const TSNetworkManagerDomain;
+
 NS_ASSUME_NONNULL_BEGIN
 
 @interface TSNetworkManager : NSObject

src/Network/API/TSNetworkManager.m

@@ -1,9 +1,5 @@
 //
-//  TSNetworkManager.m
-//  TextSecureiOS
-//
-//  Created by Frederic Jacobs on 9/27/13.
-//  Copyright (c) 2013 Open Whisper Systems. All rights reserved.
+//  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
 //
 
 #import "TSNetworkManager.h"
@@ -14,7 +10,7 @@
 #import "TSVerifyCodeRequest.h"
 #import <AFNetworking/AFNetworking.h>
 
-#define TSNetworkManagerDomain @"org.whispersystems.signal.networkManager"
+NSString *const TSNetworkManagerDomain = @"org.whispersystems.signal.networkManager";
 
 @interface TSNetworkManager ()