remove redundant assignment of isDestroyed
[BUGFIX beta] Ensure aliased {{with}} blocks are not shared.

Use prototypal inheritance to ensure that the keywords available within
a `{{#with}}` block are not leaked outside the `{{/with}}`.

Added tests to prevent regression.

Closes #3652.
Closes #3753.

(@twokul && @hjdivad && @rjackson)
[DOC] Add missing link to handlebars.helpers.input in Ember.Checkbox.
Revert "Docs: Fix link in handlebars text field API"

This reverts commit c9be7cf1b968286dd507736076ff70219ad7ddee.
[DOC beta] Add specs for Ember.EventDispatcher#setup
[BUGFIX beta] Make Ember.Handlebars.makeViewHelper warning useful.

* Adds `ember-handlebars-compiler` to the list of packages that are
  tested.
* Uses `ViewClass.toString()` in the assertion thrown from
  `Ember.Handlebars.makeViewHelper`.

Example message before this change:

```
Assertion failed: You can only pass attributes (such as name=value) not bare values to a helper for a View
```

And after (using EAK resolver):

```
Assertion failed: You can only pass attributes (such as name=value) not bare values to a helper for a View found in 'appkit@component:api-file-link:'
```
[BUGFIX beta] Fix issue with Ember.Test.unregisterHelper.

* `Ember.Test.unregisterHelper` will currently error if the helper being
  removed is found within `originalMethods`. The issue is that
  `this.helperContainer` is not available from `Ember.Test` (it is in
  `Ember.Application`).
* `orignalMethods` has been moved into a private property of the
  `Ember.Application` instance (so that we can properly restore the
  original value).
* Added a few tests for the behavior of `registerHelper` and
  `unregisterHelper`.
Update backburner build
[FEATURE ember-testing-simple-setup]

Removes the need for most of the ceremony of setting up an application for testing. The following
examples are equivalent:

Ember 1.0.0 type testing setup:

```javascript
App = Ember.Application.create();
App.setupForTesting();
App.injectTestHelpers();
```

New simple setup:

```javascript
App = Ember.Application.create({testing: true});
```
Merge pull request #3785 from rjackson/enable_simpler_testing_setup

[FEATURE ember-testing-simple-setup]
Remove feature flags for 'ember-routing-didTransition-hook'.
Remove feature flags for 'ember-routing-loading-error-substates'.
Remove feature flags for 'ember-runtime-sortBy'.
Remove feature flags for 'container-renderables'.
Remove feature flags for 'link-to-non-block'.
Remove feature flags for 'reduceComputedSelf'.
Components are lazily looked up.
Fix incorect removal of 'ember-routing-loading-error-substates'.
[FEATURE ember-testing-routing-helpers]

Adds `currentRouteName`, `currentPath`, and `currentURL` testing helpers.
Merge pull request #3711 from rjackson/add_route_testing_helpers

[FEATURE ember-testing-routing-helpers]