Changes:
- Fixed #345
- Added cron style task scheduling @progamernoob
- Added snapshot environments to the output of the API endpoint
/api/v2/repo/<REPO_ID>@KayTeeFive - Added a setting to customize retry attempts for package download during mirroring #338
- Moved statistic charts to /stats/repo/
- Removed deprecated security headers from nginx config
- Code refactoring and cleanup, typo fixes
- Various UI fixes and improvements