Support for navigation in lifecycle methods.

Fixes ERRAI-516
Allow any class that implments IsWidget to be annotated with @Page

Fixes ERRAI-486
Support for navigation in lifecycle methods.

Fixes ERRAI-516
Removed unused, unresolvable import from new test class
Merge branch 'ERRAI-486' of github.com:jbarop/errai into 2.4

Conflicts:
	errai-navigation/src/main/java/org/jboss/errai/ui/nav/client/local/Navigation.java
	errai-navigation/src/test/java/org/jboss/errai/ui/nav/client/local/PageLifecycleTest.java
	errai-navigation/src/test/java/org/jboss/errai/ui/nav/client/local/testpages/PageAWithRedirect.java
Fixed grocerylist demo: introduced cascade merge from item to department and merge grocerylist instead of persist
data-binding: fixed problem when reusing proxies in ListWidget