Fix send file length always zero (#1175)

* HttpStream must be read prior to knowing it length

We also need to create the send prior to saving the stream so we
have well defined save location. Solve chicken-and-egg problem by saving
the Send twice. This also allows for validation that the stream received
is the same length as that promissed by the content-length header

* Get encrypted file length from request

src/Core/Models/Api/Request/SendRequestModel.cs

@@ -13,6 +13,7 @@ namespace Bit.Core.Models.Api
     public class SendRequestModel
     {
         public SendType Type { get; set; }
+        public long? FileLength { get; set; }
         [EncryptedString]
         [EncryptedStringLength(1000)]
         public string Name { get; set; }