Multicolumn enrollment dialog
    
    The enrollment dialog has been modified to use scrollable tables that
    supports multiple columns to display the search results and selected
    entries. The columns are specified by calling create_adder_column()
    on the association facet. By default the tables will use only one
    column which is to display the primary keys.
    
    The following enrollment dialogs have been modified to use multiple
    columns:
     - Group's member_user
     - Service's managedby_host
     - HBAC Service Group's member_hbacsvc
     - SUDO Command Group's member_sudocmd
    
    The ipa_association_table_widget's add() and remove() have been moved
    into ipa_association_facet so they can be customized by facet's
    subclass. The ipa_table's add_row() has been renamed to add_record().
    
    Some old code has been removed from ipa_facet_create_action_panel().
    The code was used to generate association links from a single facet.
    It's no longer needed because now each association has its own facet.
    
    The test data has been updated. The IPA.nested_tabs() has been fixed
    to return the entity itself if IPA.tab_set is not defined. This is
    needed to pass unit test.