Single File Generator support

[davkean]

1. Double-click on a resx file
2. Add a new resource

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Microsoft Visual Studio
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The method or operation is not implemented.
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OK   
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[333fred]

I'll be taking notes here as I discover potential issues.

• The ResourceDesigner currently expects the IVsHierarchy to implement IVsSingleFileGeneratorFactory, which ProjectNode does not. Once we have COM Aggregation, we'll be able to directly implement this interface on the ProjectNode instance ourselves.

[davkean]

It looks like CPS has some support for single file generators, it looks like we need:

1. Define the "SingleFileGenerators" capability
2. Add registration to register the single file generator for all the files generators we are interested in, for example:

[$RootKey$\Generators\{8bb2217d-0f2d-49d1-97bc-3654ed321f3b}\DotNetPublicResXFileCodeGenerator]
@="DotNetPublicResXFileCodeGenerator"
"CLSID"="{3ade0602-cba7-4507-a207-c13e242b4f81}"
"GeneratesDesignTimeSource"=dword:00000001
"InputFileExtension"=".resx"  

[davkean]

Above you should replace the registration with the same registration as csproj.

[davkean]

We'll also need to implement IVsSingleFileGeneratorFactory - and probably just give that to CPS.

[davkean]

I've turned this into representing all single file generator support.

[333fred]

Ok, so the results of my investigations are this:

1. CPS will generate the pkgdefs for us. They have an article on adding SFG's here: https://github.com/Microsoft/VSProjectSystem/blob/master/doc/scenario/add_single_file_generator.md
2. An important note on this: the SFG must be in the same assembly as the VsPackage used to generate the pkgdefs. The resulting pkgdef will specify loading the from the assembly that the attributes were declared in. So, the C# ResX generators need to be in the ProjectSystem.CSharp.VS assembly, and similar for VB. We'll need to think about how to go about organizing our dependencies to share as much code between them as possible.
3. I'm not sure that a IVsSingleFileGeneratorFactory is necessary, other than to tell the resource designer to enable the combobox, as CPS instantiates our SFG's for us. Do we want to restructure the designer such that it doesn't need this to enable that?