Add InAppPurchase and FailedPurchase model, IapHandler module

DESC:
[Feature]
1. Add InAppPurchase and FailedPurchase model, IapHandler module
(1). Add InAppPurchase and FailedPurchase model to record In-App
Purchases information.
(2). Add IapHandler module to handle the IAP purchase flow.
(3). Add iap_info in IapError.