[CORE-3492] Order: Affiliate Orders - Blesta

Details

When someone uses an affiliate link to place an order, that order should be recorded as a referral on behalf of the affiliate.

When someone uses an affiliate link, we must set a cookie on the user's browser to reference that affiliate
- The referral link can be at /order/a/1234567/ where 1234567 is the affiliate ID
- This cookie will be referenced on client signup and order completions in order to process affiliate referrals
When an order is completed, the total cost (minus tax) should be used as the basis to determine the commission amount, and a referral should be created in the system

Note: you cannot refer yourself for orders, so any cookie that would be created for visiting the affiliate URL on your own behalf should be ignored.