-First crack at for-all, taking advantage of index
-insert-new! now returns the index it inserted
-removed select and matching? in favor of the unification approach and for-all
-if you need efficient selects, use lookup, otherwise for-all is more flexible and easier to write
-Both for-all and lookup now take advantage of partial indices
-Inlined some of the smaller and more frequent unify functions
-Removed test-data section from unify.lisp
-Need to do something about performance of for-all (some incremental tuning might do, but I get the feeling I'll need to do a deeper re-structure)