Add support for setting creation time via mk_transaction helper.
Merge branch 'develop' into feature/issue-1086-management-command-for-transaction-archiving

Conflicts:
	go/billing/tests/helpers.py
	go/billing/tests/test_tasks.py
Add helper for setting up s3 buckets.
Use s3 bucket setup helper in billing task tests.
Add transaction archiving management commmand.
Pass dates to archive_transactions and clean up command output.
Merge branch 'feature/issue-1086-management-command-for-transaction-archiving' into develop