Export improvements - custom date ranges, and more

We've made a few improvements to data exports based on your feedback:

Custom date ranges
You can now choose a custom date range when exporting any type of data. Just select 'Custom' from the list of date range options, and then enter your own start and end dates.

Limit job history to a specific round
When exporting job history, you can now limit the results to a specific round, or jobs with no round.

More fields included
We've added more fields to the exports, including the customer's balance when exporting job history.

We've also fixed a bug where the customer export would sometimes only include one job per customer. You'll now always see a row for each job a customer has.

Thanks to everyone who suggested these improvements. Keep them coming!