Another QDDIM issue

NextServiceAfterMeter is defined as a subclass of NextService.  However,
this is not strictly correct since it adds another identifying/key
property - MeterResult.  For example, both in-profile and partially
conforming traffic could go to the same FollowingService.  This would
require that NextServiceAfterMeter distinguish between instances based on
the MeterResult.

For this reason, it should subclass from nothing but have similar semantics
to NextService.

Andrea