Membership ephemeral entry and initial leader election

Also:
- env.sh to load what's needed for dev
- refactored main
- async consul client instead of blocking
diff --git a/env.sh b/env.sh
new file mode 100644
index 0000000..19c99fa
--- /dev/null
+++ b/env.sh
@@ -0,0 +1,9 @@
+# sourcing this file is needed to make local development and integration testing work
+
+# load local python virtualenv 
+. venv/bin/activate
+
+
+# assign DOCKER_HOST_IP to be the main ip address of this host
+export DOCKER_HOST_IP=$(python voltha/nethelpers.py)
+