Issue title: {{outlet.someProp}}
 Issue body: There has been some loose ideation around using `outlet` is a keyword that allow a dev to access the routable component above it. Some example usage of this:

```
{{! in the layout of an arbitrarily deeply nested component }}
{{outlet.model.name}}
{{if (some-helper outlet.someState) 'foo'}}
```

The use cases for this are poorly defined though. If any are discovered we should discuss them here.

 Comments: 
 Comment 0: An addition to this RFC i'd like to see (or perhaps a different one, although related) is to add a implicit name to the outlet (similarly to the property `name` in functions standarized in ES6).

That could, among other things, allow to infer properties based on the context. Some that come to mind are translations that come to mind are contextual translations *à là rails* (`{{t .header}}`) or links to the parent outlet regardless of where they are rendered.
 Comment 1: I'm doing some issue gardening 🌱🌿 🌷 and came upon this issue. Since it's quite old I just wanted to ask if this is still relevant? If it isn't, maybe we can close this issue?

By closing some old issues we reduce the list of open issues to a more manageable set.
 Comment 2: I'm closing this due to inactivity. This doesn't mean that the idea presented here is invalid, but that, unfortunately, nobody has taken the effort to spearhead it and bring it to completion. Please feel free to advocate for it if you believe that this is still worth pursuing. Thanks!
{'source': 'GithubIssues', 'repo_name_with_owner': 'emberjs/rfcs', 'issue_id': 95958576, 'repo_stars': 771.0}