Some fixes to lists helper to reduce mutation.
Some fixes to lists helper to reduce mutation.

Also added some TODO's to describe the plan.

Patch by: Dan Bentley

--HG--
extra : convert_revision : svn%3A32761e7d-7263-4528-b7be-7235b26367ec/trunk%402770

rhyolight/nupic.son,rhyolight/nupic.son,rhyolight/nupic.son