Added VB.Net Native Type and associated service

I saw that you have recently added an F# code generator to the Native Types feature, so to help out, I have taken the C# code generator and reworked it to provide one for Visual Basic .NET.  I have not attempted to compile the generated code, but everything appears to be correct when I run it against the RockStar Example's API and read the code. This change added the Microsoft.VisualBasic dependency to convert the underlying type to it's VB.NET name. If you don't want this dependency, I guess a static class could be created to provide the same result.

One thing that may need reviewing is the Config.TypeAlias functionality. Not sure if this configuration option needs to be changed to provide one for each language, or if some other approach needs to be taken because the alias may be different between each language for the same types.