Added: Sort clause for sections
Added: DatePublished sort clause for Solr
Added: methods to enqueue operations to be run at transaction commit
Added: more aliasing
Added: Implementation of the MultipleStringField
Changed: commenting code that doesn't work yet

Object states does not seem to be implemented completely, commenting for
now.
Changed: adapted Solr fixtures against results received
EZP-21103: Added router to valueObjectVisitor
EZP-21103: Refactored ContentTypeGroup VOV + test
EZP-21103: Refactored router testing in VOV tests
EZP-21103: Refactored Version VOV + test
EZP-21103: Refactored VersionInfo VOV + test
EZP-21103: Refactored UserSession VOV + test
EZP-21103: Refactored VersionList VOV
EZP-21103: Refactored UserRefList VOV + test
EZP-21103: Refactored UserGroupRefList VOV + test
EZP-21103: Refactored URLWildcardList VOV + test
EZP-21103: Refactored ContentList VOV + test
EZP-21103: Refactored URLWildcard VOV + test
EZP-21103: Refactored URLALias VOV + test