Upload artifacts to a web site using credentials binding

Currently PR #581 for Jenkins automation is on hold, waiting for the final step on the checklist: uploading the compiled artifacts to the distribution site. I suggest that we move that requirement to a separate issue.

There are three different situations:

1. Official Aseba releases. A version tagged release-* could be uploaded to https://github.com/aseba-community/aseba/releases using a command-line tool like github-release.
2. Nightly builds and PRs. These could be uploaded to the existing archive of nightly builds. (For those developers who don't already have access to the CI platform.)
3. Official Thymio.org releases. These should be put together by the Thymio team and may include components that aren't a part of aseba-community. So these artifacts should not be uploaded by the Jenkins automation.