The singleton service that represents the top level router was called
`$router` but this is confusing since there are actually lots of routers,
which depend upon where you are in the DOM. This is similar to the situation
with scopes.
This commit clarifies this singleton by renaming it to `$rootRouter`.
BREAKING CHANGE:
The `$router` injectable service has been renamed to `$rootRouter`
BREAKING CHANGE:
Previously, route configuration took a controller constructor function as the value of
`component` in a route definition:
```
$route.config([
{ route: '/', component: MyController }
])
```
Based on the name of the controller, we used to use a componentMapper service to
determine what template to pair with each controller, how to bind the instance to
the $scope.
To make the 1.x router more semantically alligned with Angular 2, we now route to a directive.
Thus a route configuration takes a normalized directive name:
```
$route.config([
{ route: '/', component: 'myDirective' }
])
```
BREAKING CHANGE:
In order to avoid name collisions, lifecycle hooks are now prefixed with `$`. Before:
```
MyController.prototype.onActivate = ...
```
After:
```
MyController.prototype.$onActivate = ...
```
Same for `$canActivate` (which now lives on the directive factory function),
`$canDeactivate`, `$canReuse`, and `$onDeactivate` hooks.
