This patch adds limited support for .NET SDK to the First App tutorial.
Because the "official" .NET SDK has very limited functions to call
OpenStack API, so I decided use another .NET SDK from
https://github.com/openstacknetsdk/openstack.net, It still has not full
features to support all the steps though, it will be a good start to
show people how to use C# to develop an OpenStack Cloud App.
Change-Id: I0f7d731ffd119383bd915d980e6245265cc866ca
Partial-Bug: 1449333
66dbd3e86a