revert ng:view sync caching

sync caching in ng:view must be reverted becase ng:view uses
$route.onChange to listen for changes.

$route fires all onChange events before it calls $become(Controller)
which means that if the template being included via ng:view contains
ng:controller, ng:include or other widget that create new scopes,
these scopes will be created and initialized before the parent scope
is fully initialized (happens after $become is called).

For this reason ng:view must be async.

The new scope implemenetation will resolve this issue by providing
us with an api to register one-off tasks to be executed during the
flush phase. We'll be able to compile and link the included template
safely at this time.