Add filter for releases to Prod-Stats

Detailed bug description:
Data becomes greater with each passing month and each release.
Excel supports only 1 000 000 strings. "keystone_user" file for May already contains 700 000 strings.

So I suggest to add filter for releases to https://product-stats.mirantis.com/reports.html
Thus we can decrease a size of each report.
Should be ability to download data for several releases.

Expected results:
1. Open https://product-stats.mirantis.com/reports.html
2. User can choose period and concrete release
3. Downloaded data contains info only for selected period and release