Do not show inherited memebers in autodoc by default

This is making our documentation real ugly and bloated. For example: https://www.idiap.ch/software/bob/docs/latest/bob/bob.bio.face/master/implemented.html#module-bob.bio.face.algorithm

Also, one more thing I have noticed is this failed attempt in codes to remove this bloat: https://gitlab.idiap.ch/bob/bob.bio.face/blob/58e9db9310b3ceeaea30c6825bb256682bbceee6/bob/bio/face/algorithm/Histogram.py#L167 while the problem actually lies in autodoc_default_flags in doc/conf.py.

ping @mguenther @andre.anjos