Resolve issues leftover from rebase.

- remove duplicate compile sources
- sync dynamic and static framework umbrella headers
- rename BUYClient+Checkout helpers category to avoid duplicate name

Mobile Buy SDK/Mobile Buy SDK/Buy.h

@@ -66,7 +66,6 @@ FOUNDATION_EXPORT const unsigned char BuyVersionString[];
 #import <Buy/BUYClient+Customers.h>
 #import <Buy/BUYClient+Checkout.h>
 #import <Buy/BUYClient+Storefront.h>
-#import <Buy/BUYClient+Checkout.h>
 #import <Buy/BUYRequestOperation.h>
 #import <Buy/BUYError.h>
 #import <Buy/BUYError+BUYAdditions.h>

Mobile Buy SDK/Mobile Buy SDK/Payment Providers/BUYClient+CheckoutHelpers.h

 //
-//  BUYClient+Checkout.h
+//  BUYClient+CheckoutHelpers.h
 //  Mobile Buy SDK
 //
 //  Created by Shopify.

Mobile Buy SDK/Mobile Buy SDK/Payment Providers/BUYClient+CheckoutHelpers.m

 //
-//  BUYClient+Checkout.m
+//  BUYClient+CheckoutHelpers.m
 //  Mobile Buy SDK
 //
 //  Created by Shopify.
@@ -28,7 +28,7 @@
 
 @implementation BUYClient (CheckoutHelpers)
 
-- (NSURLSessionDataTask *)handleCheckout:(BUYCheckout *)checkout completion:(BUYDataCheckoutBlock)completion
+- (BUYRequestOperation *)handleCheckout:(BUYCheckout *)checkout completion:(BUYDataCheckoutBlock)completion
 {
 	if ([checkout hasToken]) {
 		return [self updateCheckout:checkout completion:completion];

Mobile Buy SDK/Mobile Buy SDK/Static Framework/Buy.h

@@ -29,19 +29,11 @@
  */
 
 #import "BUYAccountCredentials.h"
-#import "BUYApplePayAdditions.h"
-#import "BUYApplePayHelpers.h"
 #import "BUYAddress.h"
 #import "BUYCart.h"
 #import "BUYCartLineItem.h"
 #import "BUYCheckout.h"
 #import "BUYCheckoutAttribute.h"
-#import "BUYClient+Test.h"
-#import "BUYClient.h"
-#import "BUYClient+Customers.h"
-#import "BUYClient+Storefront.h"
-#import "BUYClient+Checkout.h"
-#import "BUYRequestOperation.h"
 #import "BUYCollection.h"
 #import "BUYCreditCard.h"
 #import "BUYCustomer.h"
@@ -59,6 +51,7 @@
 #import "BUYShop.h"
 #import "BUYTaxLine.h"
 
+#import "BUYApplePayAdditions.h"
 #import "BUYApplePayHelpers.h"
 #import "BUYApplePayPaymentProvider.h"
 #import "BUYPaymentController.h"
@@ -68,6 +61,8 @@
 #import "BUYClient.h"
 #import "BUYClient+Customers.h"
 #import "BUYClient+Checkout.h"
+#import "BUYClient+Storefront.h"
+#import "BUYRequestOperation.h"
 #import "BUYError.h"
 #import "BUYError+BUYAdditions.h"
 #import "BUYManagedObject.h"
@@ -80,6 +75,7 @@
 #import "BUYPaymentToken.h"
 
 #import "NSArray+BUYAdditions.h"
+#import "NSDate+BUYAdditions.h"
 #import "NSDateFormatter+BUYAdditions.h"
 #import "NSDecimalNumber+BUYAdditions.h"
 #import "NSDictionary+BUYAdditions.h"