Ftp fix and improvements

[fmiccolis]

Prerequisites checklist

• [x] I have read the contributing guidelines.

What is the purpose of this pull request? (put an "x" next to an item)

• [ ] Documentation update
• [x] Bug fix
• [ ] New feature
• [ ] Other, please explain:

What changes did you make? (Give an overview)

• Reduced time to upload an image to the FTP server
• Removed blocking warning in ftp_put function
• fixed QR-code generation when enable remote QR (with ftp link)
• Improved base template adding the possibility to download the gallery from the remote server

Is there anything you'd like reviewers to focus on?