Enable batch save to reduce round trips to server

[rjmurillo]

From Performance Tuning the Work Item Tracking Object Model

Every time you save a work item to Team Foundation Server, you generate a round-trip operation between the work item object model and the server. To minimize the round-trips when saving several work items, use the BatchSave method.

public BatchSaveError[] BatchSave(WorkItem [] workitems)

The method saves an array of WorkItems with far fewer round-trips.