Bug 441277 - Provide an example plugin to show how to extend DSF-GDB

Change-Id: Ic6efd321d09bfc4d62344244c419dc6b0b9758ec
Signed-off-by: Marc Khouzam <marc.khouzam@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/30660
Tested-by: Hudson CI