Add support to dav and davs schemes

[jmfernandez]

WebDAV support is needed, for download of files and directories, and future upload of results to remote places.

Proposed library is https://pypi.org/project/webdav/ , as it supports both recursive downloads and uploads

[jmfernandez]

There are two issues with https://pypi.org/project/webdav/ , which are its licence (GPLv3, incompatible with Apache2), and it does not seem to be maintained (last commit happened 6 years ago).

Candidate libraries for the client implementation would be https://pypi.org/project/webdavclient3/ or https://pypi.org/project/webdav4/ , for instance.