plug-in

Using this cleanup brings:
- It reviews the feature
 - For optimization: small memory usage reduction as the outer pointer
is removed

Change-Id: Ie2b6619e495bba162360171293577bb33915d0fd
Signed-off-by: Lars Vogel <Lars.Vogel@vogella.com>
Reviewed-on: https://git.eclipse.org/r/c/platform/eclipse.platform.ui/+/179061
Tested-by: Platform Bot <platform-bot@eclipse.org>