removed old nuget provider, adding integrated nuget build
moving test providers into test project
integrated NuGet into main build, modifications to build everything for .NET 4.0 (opens up back-plat)
Merge pull request #41 from OneGet/wip

Changes: Removed old nuget provider, integrated unified nuget+onegetprovider into main build, moved test providers into test project and migrated to .NET 4.0 (instead of 4.5.1)
merged with main