[ctl] Load available configurations in "cubicweb-ctl list"
Otherwise we rely on associated ctl plugins to be loaded which is arguably orthogonal to
configurations.
3.20 (06/01/2015)=================New features------------* virtual relations: a new ComputedRelation class can be used in schema.py; its `rule` attribute is an RQL snippet that defines the new relation.* computed attributes: an attribute can now be defined with a `formula` argument (also an RQL snippet); it will be read-only, and updated automatically. Both of these features are described in `CWEP-002`_, and the updated "Data model" chapter of the CubicWeb book.* cubicweb-ctl plugins can use the ``cubicweb.utils.admincnx`` function to get a Connection object from an instance name.* new 'tornado' wsgi backend* session cookies have the HttpOnly flag, so they're no longer exposed to javascript* rich text fields can be formatted as markdown* the edit controller detects concurrent editions, and raises a ValidationError if an entity was modified between form generation and submission* cubicweb can use a postgresql "schema" (namespace) for its tables* "cubicweb-ctl configure" can be used to set values of the admin user credentials in the sources configuration file* in debug mode, setting the _cwtracehtml parameter on a request allows tracing where each bit of output is produced.._CWEP-002: http://hg.logilab.org/review/cwep/file/tip/CWEP-002.rstAPI Changes-----------*``ucsvreader()`` and ``ucsvreader_pb()`` from the ``dataimport`` module have 2 new keyword arguments ``delimiter`` and ``quotechar`` to replace the``separator`` and ``quote`` arguments respectively. This makes the API match that of Python's ``csv.reader()``. The old arguments are still supported though deprecated.* the migration environment's ``remove_cube`` function is now called ``drop_cube``.* cubicweb.old.css is now cubicweb.css. The previous "new" cubicweb.css, along with its cubicweb.reset.css companion, have been removed.* the jquery-treeview plugin was updated to its latest versionDeprecated Code Drops----------------------* most of 3.10 and 3.11 backward compat is gone; this includes:- CtxComponent.box_action() and CtxComponent.build_link()- cubicweb.devtools.htmlparser.XMLDemotingValidator- various methods and properties on Entities, replaced by cw_edited and cw_attr_cache- 'commit_event' method on hooks, replaced by 'postcommit_event'- server.hook.set_operation(), replaced by Operation.get_instance(...).add_data()- View.div_id(), View.div_class() and View.create_url()-`*VComponent` classes- in forms, Field.value() and Field.help() must take the form and the field itself as arguments- form.render() must get `w` as a named argument, and renderer.render() must take `w` as first argument- in breadcrumbs, the optional `recurs` argument must be a set, not False- cubicweb.web.views.idownloadable.{download_box,IDownloadableLineView}- primary views no longer have `render_entity_summary` and `summary` methods- WFHistoryVComponent's `cell_call` method is replaced by`render_body`- cubicweb.dataimport.ObjectStore.add(), replaced by create_entity- ManageView.{folders,display_folders}