New dashboard json

Could be an initial cut, but it has all the functionality and the specs. Will need to consider caching this. Also, this is hand-written JSON. It looks pretty (output-wise) but maybe it should use a library. For now, it's ok, I think. Once caching comes in, some part of it will need to be revisited.

In the new Rails 4 app, this can be accessed as: http://SERVER:8153/go/pipelines.new_json
It was temporary, as long as we used new_json.