restore determinism to feature selection.

See comments at
https://github.com/opencog/opencog/commit/f92d21917b7dbce6a627494950031b99d8d13386
for details.
temporary hack til other things get fixed ...
randomized sort order function
find a better mixining function for randimization.
bug fix in new compare code!

When using greter, the sort order is reversed. Dohh! That explains
the mixing problem I seemed to be having...
remove comments about mixing.
clean up notes in the new code.
patch up the unit test tow work.
Merge pull request #176 from linas/moses

Moses -- deterministic feature selection fix