Made some static methods non-static: the module thety belong to is not
installed anyway.
mentioned Steve Harris as creator of Biquad coefficient calculations.
Fixed bug where fixed order settin was checked before the check was done
if the new order was the same.
Removed useless configuration setting (we're distributing headers, so
adding debug info to binaries is somewhat weird) and added "-Wall"
option to the compilers arguments.
Added (very) generic filter interface and a method that can measure the
effective impulse resonse length.
Added feature to set weight of all-pass detection.
Fixed warnings