WPMU DEV - Snapshot Pro 4.21.1

New: HTTP Authentication for password protected sites
Improvement: Snapshot Installer now identifies the host name correctly
Improvement: Global exclusions are applied by default
Improvement: Site time is displayed on when scheduling the backup
Improvement: Snapshot settings and docs link are displayed on Plugins page
Fix: Minor code quality issues

- Fix: Snapshot Installer now handles open_basedir restriction more strictly
- Fix: Minor UI fixes
- Fix: FTP destination doesn't work in Sv4 - ftplib update
- Improvement: Odd/Even rotation process
- Improvement: Changed the description for backups deletion
- Improvement: Endpoint to force force manual retention

- Fix: Improved handling of zip file during backup
- Fix: Email is not sent after export