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!