Middleware complete code with unit tests

Breaking changes proposed:
1. AuthProvider should be an instance of AuthenticationProvider
2. Removing unnecessary public methods like buildFullURL, parsePath
3. Removed Callback support for requests
4. Options that is been passed to Client.init is changed
5. Removed redundant support for OData query params (without $ support)
6. Changed access specifier for large file upload task members to protected
7. Renamed common.ts to Common.ts
Other Changes proposed:
1. Refactored unit test cases
2. Added License information in each file

Author: muthurathinam-m

lib/graph-js-sdk-core.js

@@ -0,0 +1,11 @@
+/**
+ * -------------------------------------------------------------------------------------------
+ * Copyright (c) Microsoft Corporation.  All Rights Reserved.  Licensed under the MIT License.
+ * See License in the project root for license information.
+ * -------------------------------------------------------------------------------------------
+ */
+import { Middleware } from "../src/IMiddleware";
+import { Context } from "../src/IContext";
+export declare class CustomHTTPHandler implements Middleware {
+    execute(context: Context): Promise<void>;
+}

lib/graph-js-sdk-web.js

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+/**
+ * -------------------------------------------------------------------------------------------
+ * Copyright (c) Microsoft Corporation.  All Rights Reserved.  Licensed under the MIT License.
+ * See License in the project root for license information.
+ * -------------------------------------------------------------------------------------------
+ */
+import { AuthenticationProvider } from "../src/IAuthenticationProvider";
+export declare class DummyAuthenticationProvider implements AuthenticationProvider {
+    getAccessToken(): Promise<any>;
+}

lib/spec/CustomHTTPHandler.d.ts

@@ -0,0 +1,7 @@
+/**
+ * -------------------------------------------------------------------------------------------
+ * Copyright (c) Microsoft Corporation.  All Rights Reserved.  Licensed under the MIT License.
+ * See License in the project root for license information.
+ * -------------------------------------------------------------------------------------------
+ */
+export {};