Disabled model factory injections by default.

Given that it is currently very common to use models as globals, and that `App.Post !== lookupFactory('model:post')` when factory injections are enabled, it made sense to disable model factory injections by default.

Added the flag Ember.ENV.MODEL_FACTORY_INJECTIONS to enable model injections.

Model factory injections will become the default when accessing global models is no longer a common pattern.
Update Backburner
Move ember-states into a plugin: https://github.com/emberjs/ember-states

There are no more dependencies on ember-states in Ember.js itself, or in Ember Data. If you depend on it, please use a build from the plugin's repo.
Merge pull request #3271 from teddyzeenny/model-injections

Disabled model factory injections by default.
Throw error if Ember.StateManager or Ember.State classes are used without the ember-states plugin installed
Adds Function.prototype.observesImmediately, improves docs
Make TextField and TextArea components

This allows subclasses to use `sendAction`, among other improvements
Remove moved code
Merge pull request #3275 from wagenet/immediate-observer

Adds Function.prototype.observesImmediately
Don't force a layout on registered components

Currently, components, even when registered via Ember.Handlebars.helper,
are forced to have a corresponding layout name.

This makes it impossible to have a layout-less component (wrapping a
simple tag with some event handlers, like <input>). In particular, this
make it very awkward to subclass Ember.TextField.

This change preserves the current behavior if a component is built from
a template named components/*, but doesn't force a template on
components registered manually using Ember.Handlebars.helper.
Merge pull request #3191 from emberjs/remove-ember-states

Move ember-states into a plugin
fix #2050
Ensure toString for lazy-loaded objects managed by
the container gives the proper name.