Remove ms_dotnet4 computed version's attributes

Remove computation of version's attributes in attributes/ms_dotnet4.rb
Update recipes/ms_dotnet4.rb:
- Remove use of ms_dotnet4 version's attributes
- Use node['ms_dotnet']['v4'][version] attributes
Merge pull request #2 from criteo-cookbooks/dotnet4-attributes

Remove ms_dotnet4 computed version's attributes