Closes #72

Ref #72

This adds a "branch" attribute to the rev objects.

If an "fmt" object exists with attributes "url_vcc" and/or "url_doc",
those are taken as printf formats (which should contain a single %s) and
used with the branch attributes from the revs.

Spotted by:	Dridi

If you wish to double-check:

    git show --word-diff --word-diff-regex=. $THIS_COMMIT

Now it's explicitly advertized as SHA256.

Package `varnish5` was removed, only varnish4 or varnish6 continue to exist.

Package `varnish` was removed, only varnish4 or varnish6 continue to exist.

This adds the sources for Varnish Cache 4.1.11.

Update the table of releases (6.0.2 replaces 6.0.1). The release
file was added long ago.

This "release 6.0.2" commit is big because we also announce Long Time
Support of the 6.0 branch, a new set of repositories and explain that
the packaging changes intended for 6.0.0 is not included before now.