Issue #1019 - Deeplink to NuGet Package Explorer

Basic implemetation for https://github.com/NuGet/NuGetGallery/issues/1019

Currently the NPE Addess is hardcoded - could be moved to the web.config.

Another issue: Deeplinking with Chrome seems to be buggy (see http://stackoverflow.com/questions/13670030/why-is-activationuri-null-by-using-chrome)