Redirect --test output into stdout

By default in unittest is used stderr, that is
why autopkgtests are failing in Debian [1].

http://ci.debian.net/data/packages/unstable/amd64/y/yade/20140720_182020.autopkgtest.log
Modify slightly description of save-loadVars

Doctest was producing warnings, because variables were
overwriting. Do not execute loadVars command, but let
it be in documentation.
Change stderr to stdout in greeting message.