Add WebClient to System.Net.Requests

This PR ports System.Net.WebClient to corefx.  The code is mostly taken from desktop and then cleaned up a bit stylistically.  The only major code rewrite was removing hundreds of lines of complicated APM callback-based code and replacing it with a few core async methods.  There's still plenty of more cleanup that can be done, but functionally this is sufficient. I also wrote a bunch of tests for it (~85% coverage).

1 files changed, 7 insertions, 0 deletions

diff --git a/pkg/descriptions.json b/pkg/descriptions.json
index 33a2135f6e..311636a914 100644
--- a/pkg/descriptions.json
+++ b/pkg/descriptions.json
@@ -946,6 +946,13 @@
         ]
     },
     {
+        "Name": "System.Net.WebClient",
+        "Description": "Provides the System.Net.WebClient class, which supports sending data to and receiving data from a resource identified by a URI.",
+        "CommonTypes": [
+            "System.Net.WebClient"
+        ]
+    },
+    {
         "Name": "System.Net.WebHeaderCollection",
         "Description": "Contains types that represent HTTP request and response headers. This library is used with classes such as System.Net.HttpWebRequest and System.Net.HttpWebResponse and allows developers to query/edit header names/values.",
         "CommonTypes": [