Changed data logging significantly, in that for continuum data, the data

Changed data logging significantly, in that for continuum data, the data
  logging is more directly plugged into the signal-processing chain,
  rather than being a side-effect of plotting.  For spectral data, had it
  copy spectral bins into a data buffer that gets dumped once per second
  in the UI, same as continuum data.

Added --calib_coeff and --calib_offset command-line parameters to scale
  the output of the continuum detector.

git-svn-id: http://gnuradio.org/svn/gnuradio/trunk@3706 221aa14e-8319-0410-a670-987f0aec2ac5