Create Node Version Provider
Create C# Version Provider
Implement step for picking the version provider

If the file has '.cs' extension, the C# provider will be used.
If the package.json has a field named 'assemblyInfo', the C# provider will
also be used, using the field value as path to the AssemblyInfo file.
Otherwise, the NodeJS provider will be used.
Refactor setup step tests
Make use of version provider in Releasy
Use 'src/ProductAssemblyInfo.cs' as fallback for 'package.json'
Update README
Merge branch 'feature/version-providers'