Rename lib/objectutils to outils.py

Back when this was introduced, I mentioned that it breaks heavily tab
completion (ob<TAB> doesn't work anymore), but at that moment I didn't
have a suggestion what to name it. I think outils is good and short
enough, and doesn't conflict with anything else, so here it goes.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Michele Tartara <mtartara@google.com>