[NX-197] Implement download of exported events zip
Return the exported zip not the tmp file
Reuse FileCreated from wonderland (shared now with analytics)
refine genscripts to thread so we can shit events out faster
Mask viewport when exporting
Zip -> ZIP
Use application directories helper.  Notes about fixing up download directory.  Use timestamp-counter for file name.
Merge pull request #379 from sonatype/NX-197-analytics-download

REVIEW: [NX-197] Implement download of exported events zip