"Remove from content library" deletes the file from file system without warning

Steps to reproduce:

• Open Content library and click + to add custom folder
• Select some folder with e.g. images in it
• Right click the image and choose "Remove from Content library"
• ->Image is removed from Content library view and also the original image file is deleted from the file system
• I was not expecting that original file would be deleted, just that the file is not shown in Content library anymore. There is a risk that user deletes files permanently without meaning to do so. At least we should warn that file will be deleted.