* php/HAB/Pica/Record/TitleRecord.php (removeLocalRecord)
(addLocalRecord): Set and unset parent record reference.
* php/HAB/Pica/Record/LocalRecord.php (getTitleRecord)
(unsetTitleRecord, setTitleRecord): New functions. Set, get, unset
containing title record.
(addCopyRecord, removeCopyRecord): Set and unset parent record
reference.
* php/HAB/Pica/Record/CopyRecord.php (getLocalRecord)
(unsetLocalRecord, setLocalRecord): New functions. Set, get, unset
containing local record.