Instead of having a per-release backlog directory, create
a top level one that holds the last release backlog. In
a healthy project this directory is really meant to be
empty or only temporary filled.
For specs that are two releases older, the content will
be moved to an 'archive' directory, purely for the record.
Hopefully this one too will be empty.
API and Juno incubator were moved to a miscellanea
directory to finish off the cleanup.
Finally, some blueprints completed and therefore were
moved to the Liberty directory.
Change-Id: I972a9a56c038864d9c91ead6944c6b9355916668
415f1eaf5b