Changes to Ajax API Cart token format

Ajax API cart tokens will now be returned with a new format. The new format will include a prefix c1- however the API features and functionality remain unchanged. Apps and themes should be designed to handle cart tokens in any format and of any length. Treat the cart token as a random identifier that will change in the future.

Action Required: Ensure that any app and theme code is free from hard-coded assumptions (ex. Using regex to identify a cart token) on the format and structure of the cart token.