Update example to call DeviceInterfaceBase
Fix dbSpectrumBuf allocation new double() vs new double[]
Prep for Windows build

Added defines to pebbleqt.pri to select QT or Port audio.
Updated code to use audio config.
Next up: use fft config
Added FFT::Factory to use config values

Factory is a static method that returns an instance of whatever FFT method is defined in pebbleqt.pri
Replaced explicit fftw* with fft* and use FFT::Factory to create instance

Tested with FFTW, FFTCUTE, FFTOOURA
FFTCute and FFTOoura need IQ reversal in FFTForward

Tested by comparing spectrum with FFTW
Replaced fftw ref with fft and used new FFT config defines
Switch FirFilter to use FFT instead of FFTW

NOTE: Only works with FFTW configured.  Cute and Ooura Inverse functions not working correctly
FFT support for Mac Accelerate library - initial checkin
Mac Accelerate vDSP FFT support working
Bug: Now works correctly with FIR filter

Biggest error was using 2*size instead of 2*fftSize in cdft functions.  size is the number of samples in 'in' buffer
Bug:  FFTCute now working properly, except for windows

Windowing disabled, causing lost samples.  To be looked at later
Reduce signal level from QT audio to match PortAudio
Make FFTAccelerate (Apple) and QT Audio defaults

Not lowest CPU, but easiest to back port to windows