Merge branch 'dbbase' into 'master'

Mention the minimum required bob.db.base version

See merge request !144

conda/meta.yaml

@@ -34,7 +34,7 @@ requirements:
     - setuptools {{ setuptools }}
     - bob.blitz
     - bob.core
-    - bob.db.base
+    - bob.db.base >2.2.0
     - bob.extension
     - bob.io.base
     - bob.learn.activation

requirements.txt

 bob.blitz
 bob.core
-bob.db.base
+bob.db.base > 2.2.0
 bob.extension
 bob.io.base
 bob.learn.activation