#1261468 by dereine: Fix notices when relationship label is not defined and strict error on views_handler_field_accesslog_path

#1215602 by derhasi: Provide a views_get_views_as_options which allows to list all views availible for form elements

This reverts commit ee7707a3.

#1207680 by damz: Don't validate if there are no options set, the values are empty and required is not set

#1189926 by dereine: Allow string filters exposed required setting to be configurable and default to FALSE

Issue #470258 by joachim after more than a year of work: Groupwise representative relationships. Or subquery relationships.