FR: Firebase Performance Web - Add config to disable global performance api hooks

### Operating System

web

### Browser Version

all

### Firebase SDK Version

0.6.4

### Firebase SDK Product:

Performance

### Describe your project's tooling

Angular app with angular cli and @angular/fire

### Describe the problem

We have many usages of the web performance api to measure timings outside of firebase.

This results in quite a bit of extra data and noise getting sent to firebase.

It would be cool to have a config that turned off the automatic logging of all web performance api usages.

### Steps and code to reproduce issue

Use the web performance api for anything. Note that all it's data is sent to firebase.

We would like to disable the automatic logging of all web performance api usages.