Shipping.ByTotal: Make grid pageable

<a href="http://community.smartstore.com/index.php?/topic/46117-shippingbytotal-plugin-failing-to-load-configure-list-with-large-number-of-entries/" rel="nofollow">Does not work with thousands of records</a>.

> Migrated from CodePlex: [Issue #432](https://smartstore.codeplex.com/workitem/432) from [mgesing](https://www.codeplex.com/site/users/view/mgesing), on 7/26/2014 8:44:48 AM
