Automate the release workflow using GitHub actions

Automate the release workflow using GitHub actions

This introduces a two-part release mechanism. A manually triggered
workflow asks for the important info like type of release (stable, rc)
and code name. It then creates a cleanly mergable pull request.

When that pull request is merged, a release is automatically tagged,
built and uploaded.

Another workflow is introduced to keep track of the deleted.files info.
This is one less chore to do on a release.

A new scheme for tags is also introduced, making all tags sortable,
regardless of their type. They follow the pattern

release-YYYY-MM-DD(<hotfixletter>|rc)

A script will be used to clean-up the existing tags.