Change template so Azure Functions bundles work

[jeffhollan]

We are removing the requirement of having .NET Core SDK installed to use extensions with functions. To use this, instead of doing func extensions install you can have a host.json that includes bundling information. The runtime can than use pre-built extensions automatically without requiring a .NET build.

We should update the archetype template to include this.

{
    "version": "2.0",
    "extensionBundle": {
        "id": "Microsoft.Azure.Functions.ExtensionBundle",
        "version": "[1.*, 2.0.0)"
        }
}

[pragnagopa]

cc @soninaren @mattchenderson

@jdneo / @Flanker32 - Can you please take look at the PR ? Let us know if you have any questions.

@jeffhollan / @soninaren - What is the ETA for bundles annoucement?