various minor tweaks for tracing before running experiments for the
IJCAR paper
started refactoring of task collections to avoid creating static
collections of tasks (those could be very large)
brought back full tracing (can be turned on by a constant in
AbstractReasonerStage)
a new experimental rule application factory which tries to avoid
one-step cycles by unwinding the trace backwards for each conclusion
being produced. For each conclusion rules can be applied (at most)
twice.