Build Using Visual Studio 2012

I noticed that when building with VS2012 this is not correctly reflected in the projects. The solution and project are generated for VS2012 but not the make file calls, also the Windows platform is not correctly updated.

This can be fixed with the following changes:

UnrealBuildTool\System\VCProject.cs - VCProject.WriteConfiguration

string BatchFilesDirectoryName = Path.Combine(ProjectFileGenerator.EngineRelativePath, "Build", "BatchFiles");
    
// --> add this
if (WindowsPlatform.Compiler == WindowsCompiler.VisualStudio2012)
{
	ProjectPlatformConfiguration += " -2012";
}
// <-- add this
    
// NMake Build command line

UnrealBuildTool\Windows\UEBuildWindows.cs - WindowsPlatform

/// Version of the compiler toolchain to use on Windows platform
public static readonly WindowsCompiler Compiler = UnrealBuildTool.CommandLineContains("-2012") ? WindowsCompiler.VisualStudio2012 : WindowsCompiler.VisualStudio2013;