adding extra StartQueryEvent. It is used mostly the same way as NewQueryEvent was originally used - before making a call to server, but this time it does not make any changes on UI except for showing search-in-progress indicator (exisitng books and number of items are preserved). The NewQueryEvent is the event which is generated just before the first result from the server is returned and it is responsbile for preparing a view for new search results by removing all items and resetting number of items