Bug 6831: Add ability to enter adding child record from parent

Bug 6831: Add ability to enter adding child record from parent

Simplifies the adding of analytical records and ensures that
the data populating the 773 tag is correct. From the host record
add child record is selected and create bib is entered to generate
a new record with host item tag populated from the parent

Caveat: currently prepare_host_field only returns a field for
MARC21. Values for UNIMARC and NORMARC can easily be added but
should be done by someone familar with those formats
and conventions

Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
To test:
- create a new record
--> if you enter a value in 001 anaytics will use that in $w for linking later
--> if you set 000/LDR 19 - Multipart resource record level to 'a' there will
be a link from the parent record to the child record later
- save your record and go to the staff detail page
- in toolbar select 'New' > 'New child record'
- check field 773, 245 and 001 from the parent record should have been copied there
- check links between child and parent in staff

Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Fixed conflicts in all 3 files.

Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>
Works properly for MARC21, and follow-up adds support for NORMARC and UNIMARC.