this constructor 'new' is called when a DBIx::OptimalQuery->prepare method 
  call is issued.

  my %opts = (
    show   => []
    filter => ""
    sort   => ""
  );

  $sth = $oq->prepare(%opts);
  - same as -
  $sth = DBIx::OptimalQuery::sth->new($oq,%opts);

  $sth->execute( limit => [0, 10]);

use DBIx::OptimalQuery; my $oq = DBIx::OptimalQuery->new( select => { 'alias' => [dep, sql, nice_name, { OPTIONS } ] }

  joins => {
    'alias' => [dep, join_sql, where_sql, { OPTIONS } ]
  }

  named_filters => {  
    'name' => [dep, sql, nice]
    'name' => { 
      sql_generator => sub { 
        my %args = @_;
        return [dep, sql, name] 
      } 
      title => "text displayed on interactive filter"
    }
  },

  named_sorts => {
    'name' => [dep, sql, nice]
    'name' => { sql_generator => sub { return [dep, sql, name] } }
  },

  

  debug => 0 | 1
);