Add Topshelf.Linux so that bottles has a *nix service runner + more.

Ok so a few things are in this pull request. ( listed by importance )

1)  Add topshelf.linux as a dependency which at runtime determines platform and configured Topshelf accordingly.

2)  Fixed relative links creating IPackageInfo with incorrect "..\\Bottles.Docs" names (src/Bottles.Tests/PackageLoaders/LinkedFolders/LinkedFolderPackageLoaderTester.cs)
This is an larger issue which as 5) proves isn't really solved for absolute paths either.

3)  update Gemfile so we get the new fuburake and bottles gems
4)  removed pak-config and data from src/Bottles.Docs/Bottles.Docs.csproj as there are neither of these ( or at least no directories so they shouldn't be being generated)
5) exclude *nix on the relative_path_of_package_use_absolute_if_rooted test case