Starting 2.7 version for voltha-helm-charts

Change-Id: I65b8b491d8f648ae7a5ce169734f3dcc89fd7958
diff --git a/VERSION b/VERSION
index 9080d9c..6886b8a 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.5.1-dev
+2.7.0-dev