Tag version 2.0.0

Also update to maven docker image
tag that is SemVer compliant.

Change-Id: I444f8ee36127af385530c5be56874ea8908e5bee
diff --git a/Dockerfile.voltha-onos b/Dockerfile.voltha-onos
index 757b01e..a19f414 100644
--- a/Dockerfile.voltha-onos
+++ b/Dockerfile.voltha-onos
@@ -14,7 +14,7 @@
 
 
 # Download and copy the specified onos apps
-FROM maven:3-jdk-8-alpine as download
+FROM maven:3.6.1-jdk-8-alpine as download
 
 # The ENV settings must be replicated below as they are not shared between stages
 ENV DOWNLOAD_ROOT=/download