Implemented the basic FM detector.

* More comments on the complex type.
* Minor changes in oscillator.
FM detector working. IO refactoring.

* The test program decodes the FM broadcast station successfully.
* Processing pool works, but needs improvement.
* Fixed bugs in Signal, FCD controller, and other places.
* Added windowing functions, moved FIR filter and oscillator into
separate "cores".
* Started work on BFO.