Add usage docs for page iterator and large file upload

Author: Vikas Dadheech

Docs/Tasks/LargeFileUpload.md

@@ -0,0 +1,40 @@
+# Large File Upload Task - Uploading large files to OneDrive.
+
+This task can be used for of onedrive's [Upload large files with an upload session](https://developer.microsoft.com/en-us/graph/docs/api-reference/v1.0/api/driveitem_createuploadsession) feature.
+
+## Creating the client instance
+
+Refer [this part](https://github.com/microsoftgraph/msgraph-sdk-objc#how-to-use-sdk) of Readme file and follow the steps to create an HTTP Client configured with authentication provider.
+
+## Uploading the file
+
+ Once you have an MSHTTPClient instance you just need to use `MSGraphOneDriveLargeFileUploadTask` class in below fashion to successfully upload the file:
+ ```
+  //Get file url
+    NSURL *fileURL = [NSURL URLWithString:[[NSBundle mainBundle] pathForResource:@"LargeFileUploadResource" ofType:@".bmp"]];
+    NSError *fileReadError;
+    //Create file data
+    NSData *fileData = [NSData dataWithContentsOfFile:[fileURL absoluteString] options:kNilOptions error:&fileReadError];
+    if(!fileReadError)
+    {
+        //Create an MSGraphOneDriveLargeFileUploadTask.
+        [MSGraphOneDriveLargeFileUploadTask createOneDriveLargeFileUploadTaskWithHTTPClient:httpClient fileData:fileData fileName:@"LargeFile" filePath:@"Documents" andChunkSize:5*1024*1024 withCompletion:^(MSGraphOneDriveLargeFileUploadTask *fileUploadTask, NSData *data, NSURLResponse *response, NSError *error) {
+            if(error)
+            {
+                //Handle any error which might have occurred during upload session creation
+                NSLog(@"There was some error while creating upload session %@",error);
+            }
+            else if([(NSHTTPURLResponse *)response statusCode] == 200 && fileUploadTask)
+            {
+                //Use successfully created fileUploadTask to upload the file.
+                [fileUploadTask uploadWithCompletion:^(NSData *data, NSURLResponse *response, NSError *error) {
+                    if(!error)
+                    {
+                        NSLog(@"Response from server %@",[NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:nil]);
+                    }
+                }];
+            }
+        }];
+    }
+ ```
+

Docs/Tasks/PageIterator.md

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+# PageIterator
+
+This task enables the consumers of the SDK to iterate through paged collections in a simplified manner.
+
+To understand the objectives and requirements for this feature in more detail, please refer [PageIterator](https://github.com/microsoftgraph/msgraph-sdk-design/blob/master/tasks/PageIteratorTask.md).
+
+## Usage
+
+### Creating the client instance
+
+Refer [this part](https://github.com/microsoftgraph/msgraph-sdk-objc#how-to-use-sdk) of Readme file and follow the steps to create an HTTP Client configured with authentication provider.
+
+### Using the MSPageIterator class
+    //Create a request for the API which will have paged collection response. For example:/me/messages
+    NSMutableURLRequest *messageRequest = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:[MSGraphBaseURL stringByAppendingString:@"/me/messages?$top=10"]]];
+
+    //Create a data task to get the initial response
+    MSURLSessionDataTask *dataTask = [httpClient dataTaskWithRequest:messageRequest completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
+        if(!error){
+            __block int itemCount = 0;
+            //If there is no error, use MSPageIterator instance to perform intra-page iteration and then onwards inter-page iteration.
+            MSPageIterator *pageIterator = [[MSPageIterator alloc] initWithData:data client:httpClient andIteratorBlock:^(NSDictionary *itemDictionary, BOOL *stop) {
+                //The itemDictionary in callback block corresponds to individual message in the list.
+                if(itemCount == 21){
+                    //You can stop the iteration in below fashion.
+                    *stop = TRUE;
+                }
+                itemCount++;
+            }];
+            //Start the iteration
+            [pageIterator iterate];
+        }
+    }];
+    [dataTask execute];
+```

README.md

@@ -166,3 +166,5 @@ And that's it. You have now successfully made call to graph server asking inform
 ## Usage Resources
 
 * [Batching](/Docs/Content/Batching.md)
+* [Page Iterator](/Docs/Tasks/PageIterator.md)
+* [Large File Upload Task](/Docs/Tasks/LargeFileUpload.md)