FIX: Conditions to force a transaction resynch are automatically detected and processed

[TobyHFerguson]

If there are payments that are in 'checkout-started' state for a while (1 day?) then it might be necessary to do a full resynch.

If on looking at the order they have paid then it is definitely necessary.

The steps are:

1. Open the form
2. Open the Payables processor (assumes Payables is installed in the browser)
3. Select Force Re-sync all Payment Updates
4. Run the Membership Management -> Process Transactions function

The Membership manual needs to be updated to describe this.

A function needs to be run that detects this condition and emails membership@sc3.club (with a link to the manual).