HOTFIX: 2016.1 2016.2 2016.3 2016.4 - Multiple Remote Carting / Americart conversion fixes:

* Optimization: removed stateful properties on shared instances of parameter classes and in turn removed locks, added a context object instead. Should be a slight performance improvement in the event of parallel requests going to the addtocart endpoint.

* Reworked AmeriCart opcode processing to determine item key by looking for a matching item parameter, separator for key is now optional like it is in AmeriCart.

* # is now supported for the item key.

* Added tests for failed opcode use cases that were fixed