Notifications preflet and notification_server

Notifications preflet:
-Use sliders instead of text fields for width and timeout
-Remove icon size choice (mini icon looks horrible)
-Consolidate both "Enable" checkboxes into one
-Fix Revert button, remove Apply button, add Defaults button
-All changes to settings saved immediately
-Live example notification message shown when settings changes are made
-Add setting for individual apps to specify whether their notifications
	should be muted
-Remove history list (to be implemented later)

BNotification class:
-BNotification records the signature and name of application that
	created it
-New functions to get source application signature and name

Notification Server:
-Notification pop up view layout fixes and bold font size fix
-Remove notifications history from AppUsage class (will be saved in
	cache instead)
-Remove vector of NotificationView objects which isn't needed
-Get source application info from notification object, not the received
	message which is not reliable

src/preferences/notifications/Notifications.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010, Haiku, Inc. All Rights Reserved.
+ * Copyright 2010-2017, Haiku, Inc. All Rights Reserved.
  * Copyright 2009, Pier Luigi Fiorini.
  * Distributed under the terms of the MIT License.
  *