Ease deployment of LibGit2Sharp based web sites #597

This PR adds a targets file, which is used as part of the nuget package (nuspec) to ensure that NativeBinaries are copied/moved to the bin folder of the output directory.
As mentioned in #597 there is one caveat of this targets build file, and that is that the NativeBinaries folder is copied to the root of the csproj folder and not removed after having been copied to the output directory, which could be another project.

If the csproj is a web application the NativeBinaries folder will be included in the bin folder when doing a Publish from Visual Studio, but again a minor quirk that the NativeBinaries folder is also included in the root. And this is **only** if the nuget is installed in the web application. If its installed in another project it won't work because its not hooking into the publishing pipeline (reason below).

It was not possible to include Publish/WebDeploy specific pipeline modifications to remove the folder in the root, as the nuget then failed to install under a standard class library (if no web application was present in the solution). I assume this is because a web application includes additional targets for the Publish/WebDeploy pipeline, which a class library project doesn't.