Added BaseMultiQueue class, a common base of the old FewToFewBiQueue class and

Added BaseMultiQueue class, a common base of the old FewToFewBiQueue class and
the new MultiQueue class.

Added MultiQueue, a lockless fixed-capacity bidirectional queue for a limited
number processes. Any process may send data to and receive from any other
process (including itself). Used for collapsed forwarding notifications.

Added CollapsedForwarding class to send and handle received collapsed
forwarding notifications using MultiQueue.

Write partial Rock pages to disk in order to propagate data from the hit
writer to the collapsed hit readers. Send collapsed forwarding notification
after data was written to disk.

Missing code to share locked StoreMap entries, kick collapsed hit readers, and
to disable notifications in no-daemon mode.