Refactor reading from the database configuration

bob/bio/face/config/baseline/arcface_insightface.py

bob/bio/face/config/baseline/dummy.py

bob/bio/face/config/baseline/facenet_sanderberg.py

bob/bio/face/config/baseline/gabor_graph.py

bob/bio/face/config/baseline/helpers.py

...o/face/config/baseline/inception_resnetv1_casiawebface.py

bob/bio/face/config/baseline/inception_resnetv1_msceleb.py

...o/face/config/baseline/inception_resnetv2_casiawebface.py

bob/bio/face/config/baseline/inception_resnetv2_msceleb.py

bob/bio/face/config/baseline/lda.py

bob/bio/face/config/baseline/lgbphs.py

.../face/config/baseline/mobilenetv2_msceleb_arcface_2021.py

...bio/face/config/baseline/resnet50_msceleb_arcface_2021.py

bob/bio/face/config/baseline/resnet50_vgg2_arcface_2021.py

bob/bio/face/config/baseline/tf2_inception_resnet.py