Manifest permission for device storage access

[silvia-ivanova-github-rep]

Description

Added permission requests and set up Manifest permissions for storage access of the current device..

Affects

@claudia3

Notes for Reviewer

1. Create and then select one/ more shelves from the library ("Bibliothek"-Fragment).
2. Then select the "Backup"-option from the menu on the top right corner.
3. A dialog window with different options (allow, deny etc.) should be displayed.

• If you select "Allow", then check if your device has access to your storage.

• If you select "Deny", a window with further information should be shown:

• If you select "Deny & don't ask again"-option and after that try to backup the data, then a message will be shown.

Check if it works. Please review & comment/approve.