Netopeer NETCONF server integration

Amendments:

- Removed local copy of golang package. Added instructions to download it.
- Removed cached files which are created when transapi is built.
- Added netopeer as a build-able Makefile component.
  Updated documentation.

Change-Id: I532e813b81a0531648c5a6bcb048208700cf57a4
diff --git a/Makefile b/Makefile
index 6f96527..0c2c0fa 100644
--- a/Makefile
+++ b/Makefile
@@ -99,6 +99,9 @@
 netconf:
 	docker build -t cord/netconf -f docker/Dockerfile.netconf .
 
+netopeer:
+	docker build -t cord/netopeer -f docker/Dockerfile.netopeer .
+
 shovel:
 	docker build -t cord/shovel -f docker/Dockerfile.shovel .