Multiple named ngView directives and attaching views to routes

Usage and purpose
=================

Routes can have a view attached via the `view` property.
Views can be named like so:
``` html

	<div ng-view="subsection"></div>
```

Then you could create a route which will update only this view:
``` js
	$routeProvider.when('/somepath', {
		templateUrl: '/section-template.html',
		view: 'subsection'
	});
```

When the url is changed to '/somepath' only views named 'subsection' would
be updated. This should be used for:

 - subsections on the page which should respond to some routes,
  other views would not be changed

 - modal dialogs with their own url, like Pinterest, Trello etc.

Different Cases
===============

 - a view has a name, but the route does not have a view set

	 * the view is not updated
	 * the route is considered to be a main route
	 * the view is a secondary view.

 - the route has a `view` property, but a view is not named

 	 * the view is not named
 	 * the route is considered to be secondary
 	 * the view is (the) main view and would update only for main routes

 - the route has a `view` property and the view is named, but
 the name does not match

 	 * the view is not updated
 	 * the view is secondary
 	 * the route is secondary - it propably updates another view

 - the route has a `view` property and the view is named with the same

 	* the view is updated regarding the template and the controller
 	associated with the route
 	* the route and view are secondary, but they are bound together

If the location is changed to a route which has a view attached, but
such view does not exist then AngularJS will do nothing and no view
will be updated.

Implementation
==============

The whole thing is happening in the `ngView` directive on
`$routeChangeSuccess` event. When the `update` function in
`ngView` is called the view is updated only if the current route
and the view match.

`$route.last` is set to the previous route when a named view is updated.
This could be used from a developer to recover the location to
a previous path corresponding to a main route.

For example if you have a modal dialog with its own url and a matching route,
when the dialog is closed you would want to recover the url to the location
of the previous main route.

`$route.interpolate()` is exposed so it could be used in such scenario to
build the path using `$route.last.params`.