reset_nobserver_impl
====================

A nobserver to handle "out of band" reset events sent between layers.  When the
triggering event is detected, a reset_at_time event is sent to targets; the 
relevant time is extracted from a sync object.

add_target
----------

	some_rno add_target target

Add `target` as a layer to be reset when a trigger event occurs.

add_sync
--------

	some_rno add_sync sync

Set `sync` as the layer whose current time should be conveyed as the appropriate
time for reset to target layers.  Under normal circumstances, this should be the
layer providing the trigger pattern.