This commit consists of:
1) Add session management to netconf
2) Modularize the rpc call
3) Improve the error handling
4) Small bug fixes

Change-Id: I023edb76e3743b633ac87be4967d656e09e2b970
diff --git a/netconf/capabilities.py b/netconf/capabilities.py
new file mode 100755
index 0000000..86873f8
--- /dev/null
+++ b/netconf/capabilities.py
@@ -0,0 +1,27 @@
+#!/usr/bin/env python
+#
+# Copyright 2016 the original author or authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+from constants import Constants as C
+
+class Capabilities:
+
+    def __init__(self):
+        self.server_caps = (C.NETCONF_BASE_10, C.NETCONF_BASE_11)
+        self.client_caps = set()
+
+    def add_client_capability(self, cap):
+        self.client_caps.add(cap)
+