Remove redundant Core::SendEvent() & NotificationEvent

[Issue#]   N/A
[Problem]  Notification event is redundant
[Cause]    Previously there was no way of telling Core to process events,
except by sending an event.
[Solution] Use the ProcessEvents() method, which was separated from Core::SendEvent()

Change-Id: I240cb24834192d1c5bc797e7c9952c1666b3f3d5
Signed-off-by: Paul Wisbey <p.wisbey@samsung.com>