[Dbix-class] More refactoring, cursor/resultset differential

[Matt S Trout]

Storage::DBI now takes SQL::Abstract queries.

My plan is to replace the convert/join _cond_resolve options that currently
generate SQL for the appropriate conditions with code that simply produces
an explicit SQL::Abstract tree with the appropriate names/values inserted.

Also, I've now abstracted the storage pretty much entirely select-wise (the
insert/update/delete was in the first part but it still returned a $sth for
selects) - the equivalent class to Class::DBI::Iterator is now
DBIx::Class::ResultSet, which keeps a DBIx::Class::Cursor object that it
uses to retrieve records.

The logic in question is still in ::Cursor itself rather than
::Storage::DBI::Cursor but I intend to correct that shortly.

-- 
     Matt S Trout           Website: http://www.shadowcatsystems.co.uk
  Technical Director        E-mail:  mst (at) shadowcatsystems.co.uk
Shadowcat Systems Ltd.