Add more documentation and write tests

bob/bio/face/annotator/__init__.py

bob/bio/face/annotator/bobipfacedetect.py

bob/bio/face/annotator/bobipflandmark.py

bob/bio/face/config/annotator/__init__.py

bob/bio/face/config/annotator/dlib.py

bob/bio/face/config/annotator/facedetect.py

bob/bio/face/config/annotator/facedetect_eye_estimate.py

bob/bio/face/config/annotator/flandmark.py

bob/bio/face/config/annotator/mtcnn.py

bob/bio/face/preprocessor/utils.py

bob/bio/face/test/test_annotators.py

conda/meta.yaml

doc/annotators.rst

doc/extra-intersphinx.txt

doc/implemented.rst

doc/index.rst

requirements.txt

setup.py