Choosing join operator for join hash (activerecord)

Hi,

a simple patch to let app developers choose to use LEFT JOIN instead
of INNER JOIN for join hashes in find. Thus, named_scopes can be used
more flexible, e.g. when defining OR'ed conditions on different
associations.

Ticket
http://rails.lighthouseapp.com/projects/8994-ruby-on-rails/tickets/2063-choosing-join-operator-for-hash-joins

Patch
http://rails.lighthouseapp.com/attachments/92545/add_join_operator_option.diff

Please have a look.

Thanks,
Steffen