Summary
-------

Set of ui components to ease data browsing.


Custom facets
-------------

RelationSwitchFacet
~~~~~~~~~~~~~~~~~~~

This facet examines current rset and selected variable and displays a
list of relations that can be traversed from the selected
variable. When the user clicks on one of those relations, he gets
redirected to the resulting page.

For instance, if the original RQL is::

    Any X WHERE X is CWUser

then the facet displays (among other relations) in_group and in_state
relations. The corresponding RQL for those relations is::

    Any G WHERE X is CWUser, X in_group G
    Any S WHERE X is CWUser, X in_state S


This facet therefore differs from other facets in that it chagnes the
RQL selection (on the left of the WHERE).

NOTE:
  while this original implementation is based on facets,
  it may not be the best choice, considering its behaviour
  differences:

  - it changes the left part of the WHERE,
  - the user gets redirected to another page,
  - the facet is not reloaded with standard ``add_rql_restrticions()``
    and ``possible_values()`` API calls but is completely regenerated
    when the facets-content-loaded event is triggered.
