* 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.

* php/HAB/Pica/Record/LocalRecord.php (containsCopyRecord): New
function. Return true if local record contains a copy record.
* php/HAB/Pica/Record/TitleRecord.php (containsLocalRecord): New
function. Return true if title record contains a local record.

Returns the first of all fields that are matched by a field selector.

of fields identified by a tag