ZF-11422: provide cascading write operations on
Zend_Db_Table_Abstract / Zend_Db_Table_Row_Abstract for
arbitrary columns   At the moment (as of ZF 1.11), cascading
write operations such as _cascadeDelete() operate on primary key
columns, seemingly due to the assumption that relationships
between database tables are established through the primary key
of the parent table only.  Why is it necessary to establish a
relationship on a column other than a primary key, you ask?
Especially in hybrid web/mobile projects, where data can be
generated through a web interface as well as in a mobile app,
you need to base your relationships on a uuid rather than an
autoincremented ID, since the sequence of IDs in the web (=
usually main) and the mobile app's database are very likely out
of sync (e.g. while the ID sequence in the mobile app has
advanced due to the generation of new data, the ID sequence of
the same DB table in the main DB will remain unchanged until the
next data synchronization. In the meanwhile, there cou