creating traced version of conclusions and completing the inference
factory class which is responsible for constructing inferences (it is
used by the tracing conclusion factory which puts inferences inside
traced conclusions).
Creating the actual (a simple concurrent centralized map-based) tracing
storage. Providing a simple mechanism for turning tracing on and off
based on a single parameter in the rule application factory (it's based
on wrapping the saturation state with its tracing version which uses a
tracing conclusion factory). The remaining bit is to subclass the
conclusion insertion visitor to add the created inferences into the
storage. 
Also extending the basic conclusion visitor interface so that it can
take arbitrary parameters, not just contexts (in our case, inferences).