Generate Platform Specific Project Files about octokit.net

[shiftkey]

Ideally, contributors would only need to add a file to Octokit.csproj and run a build script (or even better just compile the solution) and we'd automatically add it to the other projects.

A post-build step to update specific csproj files sounds like the simplest way to get things done. Only friction might be with modifying a csproj file as part of a build, but shouldn't be too hard to spike.

[haacked]

So the FAKE folks might do this

now that we are abe to detect missing files we might add a "fix it" task.

stay tuned.

[forki]

See #199