Crossovers: Added copy-constructor
GenericConfiguration: Introduced facility to prevent a lot of
boilerplate when defining configuration objects by splitting out
responsibilities and providing a mechanism for reconfiguring.
User Generic configuration mechanism in Linkwitz-Riley and Zero-phase
crossovers
Frequency: added frequency positive check with exception, after
discovering this is used many, many times. Need to rewire though.
Preparing the multiband RMS limiter.
Using Frequency::checkPositive