Easier relationship specification in Class::DBI::Loader

 The Class::DBI::Loader::Relationship module acts as a mix-in, adding the
 relationship() method to Class::DBI::Loader. Since Class::DBI::Loader knows
 how to map between table names and class names, there ought to be no need to
 replicate the names.
 .
 In addition, it is common (but not universal) to want reverse
 relationships defined for has-many relationships, and for has-a
 relationships to be defined for the linkages surrounding a
 many-to-many table.
 .
 The aim of this module is to simplify the declaration of common
 database relationships by providing both of these features.
 .
 The relationship takes a string. It recognises table names (singular
 or plural, for convenience) and extracts them from the "sentence".