releng: add LTTng RCP features to Linux Tools update sites

releng: add LTTng RCP features to Linux Tools update sites

This will allow users to base a customized RCP on the standard tracing
RCP.

Also update lisence information and update site reference in the
RCP features and plug-ins.

Change-Id: I0927095a6818f7a4079c0be05dd7c19e0b22a557
Signed-off-by: Bernd Hufmann <Bernd.Hufmann@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/24858
Tested-by: Hudson CI
Reviewed-by: Bernd Hufmann <bernd.hufmann@ericsson.com>
Tested-by: Bernd Hufmann <bernd.hufmann@ericsson.com>