Issue #340 : Remote links for single file: HTTP (fsnip, etc.) and Gist

Support for any http-source download link.
Gist also suported multiple files so it is separte from any http-source.


Usually this is not a problem as usually you know the file name you want to reference. :-) If there is just file reference e.g. "http https://example.com/some.txt" without any file-spec (file names) then it will use the last part of url as system file name (here: some.txt).