[FEATURE ember-routing-multi-current-when] Use space delimter.

* Use space for delimter.
* Enable by default.
Merge pull request #5387 from rwjblue/update-and-enable-multi-current-when

[FEATURE ember-routing-multi-current-when] Use space delimter.
Deprecate LinkView.prototype.currentWhen.

Using dasherized properties in Handlebars helpers is preferred.
Merge pull request #5388 from rwjblue/deprecate-currentWhen

Deprecate LinkView.prototype.currentWhen.
[FEATURE ember-routing-linkto-target-attribute] Enable by default.
[FEATURE ember-routing-auto-location-uses-replace-state-for-history]

Enable by default.
[FEATURE ember-metal-is-present] Enable by default.
[FEATURE ember-runtime-proxy-mixin] Remove feature (make private).

* Remove feature flags.
* Make `Ember._ProxyMixin` private API for internal use.
Merge pull request #5389 from rwjblue/enable-linkto-target-attribute

[FEATURE ember-routing-linkto-target-attribute] Enable by default.
Merge pull request #5390 from rwjblue/ember-routing-auto-location-uses-replace-state-for-history

[FEATURE ember-routing-auto-location-uses-replace-state-for-history]
Merge pull request #5391 from rwjblue/enable-ember-metal-is-present

[FEATURE ember-metal-is-present] Enable by default.
Merge pull request #5392 from rwjblue/remove-proxy-mixin-feature

[FEATURE ember-runtime-proxy-mixin] Remove feature (make private).
[FEATURE property-brace-expansion-improvement] Enable by default.

Also, updates `Ember.expandProperties` docs.
Merge pull request #5393 from rwjblue/enable-property-brace-expansion-improvement

[FEATURE property-brace-expansion-improvement] Enable by default.
Deprecate global access to view classes from templates

This deprecates accessing views as globals. These are all deprecated
cases with this patch:

    {{view "App.SomeThing"}}
    {{view Oh.ThisToo}}
    {{#each itemViewClass="Some.Wow"
    {{#each itemViewClass=Not.Yet
    {{#each itemView="Ugh.Why"
    {{#each itemView=Something.Something
{{view Ember.Select}} becomes {{view 'select'}}

This patch also introduces a syntax for accessing parts of Ember that
still rely on the global view access APIs, such as select:

    {{view Ember.Select value=whut}}

Here we have added the select control to the views namespace on the
container. This is the new syntax:

    {{view "select" value=whut}}
Prefer isPath over indexOf
Update tests to avoid global view lookup deprecation notices
Update tests to deprecate global access from templates w/ helpers
Update documentation to avoid global view access