[Feature Request] Include document path in permissions errors

### [REQUIRED] Describe your environment

* Operating System version: OS X
* Browser version: Chrome
* Firebase SDK version: (all)
* Firebase Product: Firestore

### [REQUIRED] Describe the problem

#### Steps to reproduce:

This is a feature request, so apologies for abusing the template. It would be incredibly helpful if the "Missing or insufficient permissions." error thrown by the Firestore SDK had some information on what request failed. I realize for queries this might be difficult but for simple document CRUD operations, it would be great if the error object included the document path.

Firestore is incredibly reliable so most developers are not in the habit of adding `try/catch` around most simple operations. This means when you do get an accidental error like a rules failure, it may not be caught locally and when you see the error in your app metrics it may be lacking all context. So I'd love for the Firestore SDK to help me carry that context.