New ServiceReference sort order

See #30
Shell command "sl" doesn't have to show a reversed result
Use a re-entrant lock in ServiceRegistry

... the registration of a service can imply a call to __sort_registry.
Corrected the EventAdmin test

A small bug wasn't visible due to previous ServiceReference ordering.
=> Event handlers present at posting but gone during the notification loop must/can not be notified.
Corrected bad result of __get_service in case of BundleException