#3462 Add Paging as alternative to maxRows + firstRow + orderBy

[rbygrave]

Paging is an alternative to specifying the maxRows + firstRow + orderBy on a query.

Example:

    var orderBy = OrderBy.of("lastName desc nulls first, firstName asc");
    var paging = Paging.of(0, 100, orderBy);

    new QContact()
      .setPaging(paging)
      .lastName.startsWith("foo")
      .findList();

// or ...

    DB.find(Contact.class)
      .setPaging(paging)
      .where().startsWith("lastName", "foo")
      .findList();