Put some love on FFTFrame API.

- Disable copy of FFTFrame object and add a copy method to replace
the Platform::createFFTFrame method.
- Remove useless checks for m_fftFrame.
- Remove the m_fftFrame.release() call at the destructor, the m_fftFrame will be deleted anyway.

Reviewed by: Lauro Neto
Remove FFTFrame::multiply from API and add processor optimized matrix multiplications everywhere.

Reviewed by: Lauro Neto