[#3154] ticket:384 Application methods for bulk export
 [#3154] ticket:387 Admin page for bulk export
[#3154] ticket:387 Post export task
[#3154] ticket:387 Bulk export task skeleton
[#3154] ticket:386 Config option for export dir
[#3154] ticket:386 Add file handle param to bulk_export()
[#3154] ticket:386 Pass file handles to the bulk_export()
[#3154] ticket:386 Zip exported data
[#3154] ticket:386 Don't run export if another one is running
[#3154] ticket:386 Check export status in UI
[#3154] ticket:386 Notify user when export finished
[#3154] ticket:388 Export wiki
[#3154] ticket:388 Add not exported tools to notification email
[#3154]  ticket:394 Bulk export: ForgeLink
[#3154] ticket:394 Set up context before calling bulk_export

Also, use controller's method inside ForgeLink's bulk_export()
to get app's json representation to avoid code duplication.
[#3154] ticket:394 Fix test
[#3153] ticket:389 bulk_export outline for tracker
[#3153] ticket:389 finished tickets with posts export
[#3153] ticket:389 added config to tracker bulk_export
[#3153] ticket:389 fixed tests for export