Give - Recurring Donations 2.6.0

* Fix: Resolved the "Source not found" issue for Stripe Recurring using the Checkout modal option.

* Fix: Ensure that new installs properly set the column types for subscription amounts. Previously if a admin installed recurring 1.8.5 - 1.8.6 the column type would have an incorrect decimal number which resulted in incorrect amounts displayed. This update includes an auto-upgrade check to set the column type correctly.

* New: Added a new email template tag `{subscriptions_link}` that takes donors to their subscription history.
* Fix: Links to subscription details from receipts now will never expire or require a login. This is to improve the donor experience and not require them to confirm their email or login.