[RELEASE] Released version 2.2-dev0

Released version 2.2-dev0 with the following main changes :
    - exact copy of 2.1.0
diff --git a/VERSION b/VERSION
index 7ec1d6d..cb365cc 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.1.0
+2.2-dev0