Add documentation for @Host

[jrgleason]

I'm submitting a ... (check one with "x")

[X] bug report => search github for a similar issue or PR before submitting [ ] feature request [ ] support request => Please do not submit support request here, instead see https://github.com/angular/angular/blob/master/CONTRIBUTING.md#question Current behavior If you look at the code for metadata, you will see that under HostDecorator is suggests...

For more details, see the {@linkDocs guide/dependency-injection "Dependency Injection Guide"}.

Problem is there is nothing about the @Host inside that page.

Expected behavior

We should either remove the reference to documentation, or add an appendix that speaks to this behavior

What is the motivation / use case for changing the behavior?

I am trying to create a directive that uses @Host to find a parent and looking for documentation around how the @Host annotation resolves.

From (https://github.com/angular/angular/issues/13863)

[wKoza]

An example of use @Host here : https://angular.io/docs/ts/latest/api/core/index/Host-decorator.html

For the link, maybe this link would be more appropriate :

https://angular.io/docs/ts/latest/cookbook/ts-to-js.html#!#dependency-injection