Image added (#434)

* Image added

* ImageMaximumBytes

* FileController remove Authorized

* ApplicationCore.Constants.AuthorizationConstants.AUTH_KEY

* SavePicture in the interface.

* IFileSystem in Core

* WebFileSystem in Infrastructure

* PictureUri removed from UpdateCatalogItemRequest

* Modal scroll fix

src/PublicApi/ImageValidators.cs

@@ -0,0 +1,25 @@
+using System;
+using System.IO;
+
+namespace Microsoft.eShopWeb.PublicApi
+{
+    public static class ImageValidators
+    {
+        private const int ImageMaximumBytes = 512000;
+
+        public static bool IsValidImage(this byte[] postedFile, string fileName)
+        {
+            return postedFile != null && postedFile.Length > 0 && postedFile.Length <= ImageMaximumBytes && IsExtensionValid(fileName);
+        }
+
+        private static bool IsExtensionValid(string fileName)
+        {
+            var extension = Path.GetExtension(fileName);
+
+            return string.Equals(extension, ".jpg", StringComparison.OrdinalIgnoreCase) || 
+                   string.Equals(extension, ".png", StringComparison.OrdinalIgnoreCase) || 
+                   string.Equals(extension, ".gif", StringComparison.OrdinalIgnoreCase) || 
+                   string.Equals(extension, ".jpeg", StringComparison.OrdinalIgnoreCase);
+        }
+    }
+}