Created a template that can be used to construct a Lock=free consumer
from the combination of a BusProcessor and its configuration, provided
that the configuration-type is trivial to copy.
Removed GroupVolumeConsumer as it can be easily created with
LockFreeBusProcessor.
Made the configuration of a Linkwitz-Riley crossover trival to copy.
Modified proof-of-concept, that needs to be moved somewhere else.