* added two options for dealing with Sitecore marketing campaign "first page" behavior
clarified campaign behavior statement
added example of tracing order steps for performance debugging
added performance test project for general performance issue diagnosis
added additional functionality to performance test utility for similating various item API load scenarios
make sure gift message label comes from content
initial work on invoice payment example
Manual merge of pull request from Semion McAlice of Alpha Solutions with improvements to cart persistence example.

* added enhancements so it doesn't restore on every request, only first time.
* added enhancements so it doesn't persist on every request, only if the basket has been updated.
* added configurable options for behavior when restoring from logged in customer
* added support for ajax calls, by adding pipeline steps to the mvc.* pipelines.
* added support for multiple coupon codes.

Thanks Semion!
tweaks to cart persistence
update / completion / documentation of the invoice payment example
added example of extending CustomerInfo and new account form
a small add to payment example README
Updated README for solution to include a table of contents
added README for OrderExtension project and fixed namespace of RegisterTypes
TDS v5 upgrade
Added ProductUrl example project.
Fixed typo
Discount examples project with implementation of true BOGO-style discounts
Merge remote-tracking branch 'upstream/master'

Conflicts:
	src/ActiveCommerce.Training.CartPersistence/ActiveCommerce.Training.CartPersistence.csproj
	src/ActiveCommerce.Training.CartPersistence/App_Config/Include/xActiveCommerce.xCartPersistence.config
	src/ActiveCommerce.Training.CartPersistence/Common/CartPersistenceContext.cs
	src/ActiveCommerce.Training.CartPersistence/Common/CustomerRestoreStrategy.cs
	src/ActiveCommerce.Training.CartPersistence/Pipelines/Analytics/LoadShoppingCart.cs
	src/ActiveCommerce.Training.CartPersistence/Pipelines/Analytics/PersistShoppingCart.cs
	src/ActiveCommerce.Training.CartPersistence/Pipelines/Mvc/LoadShoppingCart.cs
	src/ActiveCommerce.Training.CartPersistence/Pipelines/Mvc/PersistShoppingCart.cs
	src/ActiveCommerce.Training.CartPersistence/Pipelines/PersistCart/CheckCartUpdated.cs
	src/ActiveCommerce.Training.CartPersistence/Pipelines/PersistCart/ReadFromCart.cs
	src/ActiveCommerce.Training.CartPersistence/Pipelines/RestoreCart/ReadFromCustomer.cs
	src/ActiveCommerce.Training.CartPersistence/Pipelines/RestoreCart/SetCartUpdatedEvent.cs
	src/ActiveCommerce.Training.CartPersistence/Users/CustomerManager.cs