remove unneeded code from 11-paging.t
remove/fixup some Pg-specific code

 * DBIC.pm was checking for "no such column" errors using a Pg-specific
   regex.  Teach the regex to understand SQLite syntax, too.

 * Remove some DBI::Pg preloading code

 * Add a note to NOTES.pod that the current code needs to be tested with
   other database backends.
update 12-searching.t to work with TestSchema