* Populate push configs when parsing the vagrantfile
* Allow untyped configs to be shipped over GRPC
* In our demo plugin, walk the vagrantfile and snag the config
Example Vagrantfile that works with the demo plugin:
```ruby
Vagrant.configure("2") do |config|
config.push.define "myplugin" do |push|
push.coolkey = "coolvalue"
push.alist = ["so", "many", "items"]
push.ahash = { "hashkey" => "hashvalue" }
end
end
```
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