[DOC release] Fix template lookup documentation.

The previous documentation suggested that an `Ember.View` could specify
its `templates` property to be used for template lookup instead of using
`Ember.TEMPLATES`.

This fixes the documentation to reflect what we are actually doing for
template lookup.
Merge pull request #3648 from rjackson/split_ember_view_core_up

[DOC release] Fix template lookup documentation.