feat(net): templatized csharp sample app and moved from init to sample-app. Changed hook code to allow templating.

[gweinhold]

• Added template support for hook.js files as .NET add project should be dynamic. (Creates tmp dir in target location to allow for dynamic modification of hook file)
• Moved sample app that was in csharp init out to sample-app.
• Changed both init and sample-app projects for csharp to be dynamic (No longer hardcoded to HelloCdk)
• Addresses csharp portion of init templates for csharp/fsharp/java are in wrong category #2188

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