WIP - add testability on top of binding info changes

[juliemr]

feat(testability): add $testability service

The $testability service is a collection of methods for use when debugging
or by automated testing tools. It is available globally through the function
`angular.getTestability`.
For reference, see the Angular.Dart version at
https://github.com/angular/angular.dart/pull/1191

Other notes:

This will still require a new version of Protractor to check for the testability service and defer to that when running client side scripts. I'm happy with any combination of using this + the protractor change + the binding info change. I believe the only way to never break stuff would be

• Release a new version of protractor that checks for the $testability service and defers to it if present
• (optionally merge a version of this that works with the old binding info)
• merge this and the new binding info

[juliemr]

Updates to protractor (list item #1) done in angular/protractor@0e9c2f4 and angular/protractor@e3e2ed3, but not out in a release yet (but could be, it's a noop for current uses).

EDIT: out in release Protractor 1.1.1

[juliemr]

This is now a separate PR on top of angular.js/master: angular#8767

I will make a new one on top of the binding info changes, assuming that goes in.