Implement timeouts on actual operations

At the moment it seems that the timeout values are only used on the initial connection to a Couchbase node, not on the servicing of operations.

Comment from a customer:
We had the problems in the WaitAny/WaitMultiple part of the BulkGet method. We saw that there is no timeout passed to the Wait methods. There is a time defined on the connections itself but it would be better if the WaitAny/WaitMultiple methods would have a timeout too.