Unify conjugation order.

Currently `and*()` methods append conditions, while `or*()` methods
prepend them. While this doesn't affect the logic of the statement,
it might be confusing, and it contradicts the description.

src/Database/Query.php

@@ -1986,7 +1986,7 @@ protected function _conjugate($part, $append, $conjunction, $types)
         } else {
             $expression = $this->newExpr()
                 ->setConjunction($conjunction)
-                ->add([$append, $expression], $types);
+                ->add([$expression, $append], $types);
         }
 
         $this->_parts[$part] = $expression;