[REFACTOR] renamed classes in subscription package

The SubscriptionManager does not manage anything but just replies to
presence packets.

Furthermore the SubscriptionManagerListener is more than a dump name
because the name fails to reflect the purpose of that listener.

Change-Id: Ibb4bff74201c443df48d02dbc54dd53242bcc447
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1306
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>