Get latest items using handle

[tsega]

The get latest items functionality should work with the handles instead of the ids of the items. There an issue with just looking at the id's for items to determine if they are new or not since documents/items could exist in the system for a long time and made public at a later time.

For the CGSpace point of view these items are the recently added items. From the internal database id's point of view, however, these item were created a while ago and not really the "recently added items". So to keep things consistent, latest items definition should mean the items that have the latest handles.