Deprecate pylearn2.utils.environ.putenv -- it is equivalent to os.environ[..]

In contrast to the original comments do changes to os.environ[..] actually get inherited to child processes.

I replaced all calls to utils.environ.putenv by direct changes to os.environ[..]  -- there were only a few.

pylearn2.utils.environ.py could be removed in the future; for now it just prints a deprication warning.