PortableDroid - updating references to Microsoft.Net.Http NuGet package

Updating references to Microsoft.Net.Http NuGet package to fix build errors appearing when building a Xamarin Android project after adding the Signalr Client NuGet package to the project.
Disable keep alive checks in long polling transport - JS
Timeout long polls exceeding the ConnectionTimeout on the JS client
Disable keep alive checks in long polling transport - .NET