Add custom MKStoreKitConfigs.h

Add conditional compilation to include another custom copy of MKStoreKitConfigs.h instead of the one included in the repository. This allows customizing header file for the application without changing the header file in the library source code repository.
Merge branch 'feature_custome_header' into develop
Add function to delete purchase data form iCloude during testing
Merge branch 'feature_remove_icloude_data' into develop
Add flag to know if product list fetch failed and retry every time sharedManager is retrieved until succeeds.
Merge branch 'feature_refresh_product_list' into develop
Add notification when product purchased or restored
Merge branch 'feature_product_purchase_notification' into develop
Merge branch 'develop'