pseudo-merge from pyrf/master
Merge remote-tracking branch 'pyrf/master' into waterfall

Conflicts:
	examples/waterfall_crosshair_demo.py
	pyrf/gui/waterfall_widget.py
added waterfall.set_lookup_levels and connected to rtsa-gui plot controls
tidied the last commit
Merge remote-tracking branch 'pyrf/master' into waterfall
Merge remote-tracking branch 'mfarhan/clear_trace'
Merge remote-tracking branch 'rwarren/waterfall'
created branch to hold 2.4.0-beta release
Merge remote-tracking branch 'mfarhan/ui_improvements'
Merge remote-tracking branch 'mfarhan/trigger_fix'
set REFLEVEL_ERROR when old firmware detected
Merge pull request #1 from wardi/removed_fft_constants

set REFLEVEL_ERROR when old firmware detected
Merge remote-tracking branch 'mfarhan/removed_fft_constants'
added HDR gain control to thinkRF API, and device properties
added HDR gain controls to device controls panel
limited hdr gain control to -10 - 0
added gain/attenuation controls to amplitude group box
removed whitespace
fixed merge conflicts of hdr gain controls
created a amplitude controls class