[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 beta] Add specs for Ember.EventDispatcher#setup
Remove duplicate changelog entry.
Merge pull request #3769 from pangratz/add/specs_for_event_dispatcher

[DOC beta] Add specs for Ember.EventDispatcher#setup
Merge pull request #3754 from rjackson/use_new_context_for_with_helper

[BUGFIX beta] Ensure aliased {{with}} blocks are not shared.
Merge pull request #3806 from ugisozols/remove_dup_changelog_entry

Remove duplicate changelog entry.
Add a helpful warning

Because almost every property on a class definition is a function, it's
easy to accidentally say this out of habit:

````javascript

App.MyController = Ember.Controller.extend({
  actions: function() {
    doThing: function() { ... }
  }
});

````

When you meant to say this:

````javascript

App.MyController = Ember.Controller.extend({
  actions: {
    doThing: function() { ... }
  }
});

````

This doesn't product any errors or warning, it just makes your handlers
invisible. My change adds an assertion.
Merge pull request #3749 from ef4/actions-warning

Actions warning
Fixes incorrect truncation
Merge pull request #3811 from twokul/fix-for-set-path

Fixes incorrect truncation
Adds truncation tests
Merge pull request #3812 from twokul/truncation-tests

Adds truncation tests
[BUGFIX beta] Make flag LOG_TRANSITIONS_INTERNAL work again

The `router.log` method is set to `Ember.Logger.debug` when the
LOG_TRANSITIONS_INTERNAL flag on the application is set. Since the
`namespace` at the time of the check is `undefined`, this doesn't work.

This fix moves the check into the routers' `init` method.

This closes #3813
Merge pull request #3814 from pangratz/fix/router_LOG_TRANSITIONS_INTERNAL

[BUGFIX beta] Make flag LOG_TRANSITIONS_INTERNAL work again
[FEATURE with-controller] {{#with}} can take a controller= option

Wrap the context with an Ember.ObjectController
Merge pull request #3722 from bcardarella/bc-with-controller-option

[FEATURE with-controller]: {{#with}} can take a controller= option
Added warning when using deprecated helpers and removed bindAttr/linkTo references
Merge pull request #3826 from marcioj/warning_in_deprecated_helpers

Added warning when using deprecated helpers and removed bindAttr/linkTo references