Protocomm : Added component core for protocol communication

* This manages secure sessions and provides framework for multiple transports.
* The application can use protocomm layer directly to have application specific extensions for provisioning (or non-provisioning) use cases.
* Following features are available for provisioning :

  * Security - Security0 (no security), Security1 (curve25519 key exchange + AES-CTR encryption)
  * Proof-of-possession support for Security1

* Protocomm requires specific protocol buffer modules for compilation which can be generated from the `.proto` files in the `proto` directory using make.

Co-Authored-By: Amey Inamdar <amey@espressif.com>
Co-Authored-By: Anurag Kar <anurag.kar@espressif.com>

components/protocomm/include/security/protocomm_security0.h

@@ -0,0 +1,25 @@
+// Copyright 2018 Espressif Systems (Shanghai) PTE LTD
+//
+// 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.
+
+#pragma once
+
+#include <protocomm_security.h>
+
+/**
+ * @brief   Protocomm security version 0 implementation
+ *
+ * This is a simple implementation to be used when no
+ * security is required for the protocomm instance
+ */
+extern const protocomm_security_t protocomm_security0;