Adds switch for upgrade in checkout; adds upgrade domain to cart.
Update entire codebase to start accommodating new db structure to allow more scalability for partner examples
Updated the checkout process for upgrades.
Updated integration and checkout pages.

1. Added read me,
2. Database comments and updates
3. Cleaned up the account centre
4. Cleaned up the configs
Merge branch 'checkout_upgrade' of https://github.com/basekit/partner-php into feature/AZTEC-1180

Conflicts:
	library/PartnerWeb/Controller/CheckoutController.php
	library/PartnerWeb/Controller/PlansController.php
Fixed wrongly named input fields