Improved download_attachments_from_page: added filename filter for si… (#1476)

* Improved download_attachments_from_page: added filename filter for single-file-download and in-memory BytesIO option (for pandas loading) in addition to writing to disc.

* Hotfix: Changed save_path back to path for fully backwards compatibility

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Co-authored-by: Anders Imenes <anders.imenes@telenor.no>