remove NOISEFLOOR_CALIBRATION and ADC_DYNAMIC_RANGE constants

replace with REFLEVEL_ERROR and normalized reflevel calculation
HDR usable bins good, SH+fshift not
remove forgotten code
remove dead code
better hdr bottom and min dbm settings
Merge pull request #34 from wardi/remove-adc-constants

remove NOISEFLOOR_CALIBRATION and ADC_DYNAMIC_RANGE properties
Merge branch 'ui-improvements'

Conflicts:
	pyrf/gui/gui.py
	pyrf/gui/plot_widget.py
set level trigger to 1/2 of span by default
fixed init without xdata in model; mouse move handling now optional; added mouse click handling
fixed resize bug
Merge remote-tracking branch 'rwarren/waterfall' into ui-improvements