[6.x] Respect the listing sort order when exporting form submissions

[aerni]

Issue

Form submission exports ignored the listing's sort order.

The sort was only sent when you picked Filtered Submissions, and that option is disabled unless a search or filter is active. And the default date sort didn't count. So the common case, open a form and hit export, always gave you an arbitrarily ordered file.

Behavior changes

• All Submissions now exports in the listing's sort order, including the default date sort. It was previously unordered.
• Filtered Submissions is now only enabled when a search or filter is active. A changed sort used to enable it, but the sort applies either way now, so it would return the same file.

Also

The Filtered Submissions description claimed exports respect the visible columns. They don't, so I dropped that half of the sentence.