Openvariant | Don't fail if folder/file permission denied

[FedericaBrando]

When iterating through a folder path, it would be nice to have a list of reported folder that have been skipped because of permission denied error, instead of just fail and exit. And returning a warning everytime a folder is skipped because of this.

This can also happen when a folder has symlinks from a folder not accessible to a user. it would be nice to check if those symlink are because the file does not exists or it is not accessible because of the error previously described.

In this way, when iterating in a big folder, with multiple datasets, we can run openvariant without worrying too much of permissions, as long as we have a detailed track of the folders and file skipped.

Adding a flag like --skip to make this feature running could be helpful.