Gateways should show if there's a total

In a case where an item has a fee but ends up being zero (e.g. discount) the user should be able to purchase.

Note: Untested and I'm assuming gateway some logic/integrations could fail.
Pass the discounts array to the filter.

Allow for filters to know as much as the function.
Refactor edd_record_sale_in_log() to properly respect payment date. #2600
Merge branch 'master' of github.com:easydigitaldownloads/Easy-Digital-Downloads
Add descriptive_text as a settings type
Add seq_id key
Slight fix
Correct payment export goofs in previous commits from @chriscct7. #2605
Fixes #2606
Rework price options output to fix issue when default option not being checked. Closes #2602
Merge branch 'master' of github.com:easydigitaldownloads/Easy-Digital-Downloads
Default download ID. #2592
remove accidental addition. #2592
Rework logic in edd_price() to find the lowest price. Closes #2592
Rework edd_apply_preset_discount(). #2607
Merge branch 'master' of github.com:easydigitaldownloads/Easy-Digital-Downloads
Return false if  is empty. Fixes #2608
Improved unit tests for #2608
Merge pull request #2604 from leewillis77/master

Add descriptive_text as a settings type
Update @since tag for edd_descriptive_text_callback