webadmin,userportal: Synchronize refresh.

- Added logic to automatically refresh the current active
  model when an action completes or when an event is found
  during the event query (webadmin).
- When an action completes, have the currently active models
  start to poll quickly for a short period of time in case
  and action completed after the call returned.
- Added event bus to the models. With associated event handling.
- Automatically clear event handlers when the user logs out.
- Refactored logout sequence to be simpler and extracted common
  code between webadmin and user portal.

Change-Id: Iaa59712f8f74426b0ca6a132664167f42fb8d7b2
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=858166
Signed-off-by: Alexander Wels <awels@redhat.com>