[v6r12] Add getBulkRequest feature

Allows to get several Requests from the DB at once. 

The requests returned are the oldest. It used to be the same for getRequest, but it now takes a random request from the 100 oldest and 50 newest. I did not find a clever and efficient way to do that in the bulk query. 

The RequestExecutingAgent is capable of using this feature, based on a new CS switch:
if BulkRequest == 0, then it will use getRequest and run as before. Otherwise, it will get (BulkRequest value) requests at once