Support bundling extensions from Marketplace at build time

[joaomoreno]

cc @weinand @roblourens

• Query bundled extensions
• Bundle extensions at build time
• Prevent installation of these extensions from the Marketplace

[joaomoreno]

@weinand @roblourens

https://github.com/Microsoft/vscode/blob/master/build/gulpfile.vscode.js#L40