------
- Added support for the Classic Cataclysm beta.
CLI
~~~
- Relocated plug-in commands under ``plugins``.
- Removed ``--retain-strategies`` flag from ``update`` command.
Strategies are now always respected when present; to force an update with
the default strategy set, append ``=`` to the add-on definition.
- Global ``-d/--debug`` flag renamed to ``-v/--verbose``.
- ``configure --show-active`` sub-flag reimagined as the ``debug`` command.
- Allow filtering installed add-ons by source using ``list source:``, replacing
"source" with the source identifier.