SampleLoader as transformer

Depends on bob.pipelines!60 (merged)

ping @ydayer @amohammadi

bob/bio/face/config/database/meds.py

+from bob.bio.face.database import MEDSDatabase
+
+# In case protocol is comming from chain loading
+# https://www.idiap.ch/software/bob/docs/bob/bob.extension/stable/py_api.html#bob.extension.config.load
+if "protocol" not in locals():
+    protocol = "verification_fold1"
+
+
+database = MEDSDatabase(protocol=protocol)