[rules-dev] shadow facts

[Mark Proctor]

If we know that facts will only have their values altered in the 
consequence, during the execution of the working memory, we can dispense 
with shadow facts - instead we can alter the "setter" to do a retract 
and assert. What was the overhead of shadow facts in the end, about 10%? 
so this should help the benchmarks. This should also help with problems 
such as marcos's, where he is dealing with a million and upwards facts.

Mark