[ENHANCEMENT] Update sendToCCBill() to avoid using dynamic order pr…

[MaximilianoRicoTabo]

…operties

All Submissions:

• Have you followed the Contributing guideline?
• Does your code follow the WordPress' coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

• Get rid of initial payment from $order in favor of the subtotal taken from level retrieved through $order->getMembershipLevelAtCheckout();
• Use this level to get the info to handle recurring payments
• Get rid of Billing Period in favor of $level above and cycle_period attr
• Refactor $recurring_period to simplify

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you successfully run tests with your changes locally?

Changelog entry

Enter a summary of all changes on this Pull Request. This will appear in the changelog if accepted.