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
changed controls layout
changed names of amplitude controls to reflect more familliar SpecA controls
made labels larger, and in a bold font
grid lines are much brighter now
made text of controls darker
made plot labels bolder
bolded the fonts of groupboxes
added fonts file to gui
Merge remote-tracking branch 'pyrf/master' into waterfall
fixed max/min hold not reseting when device is retuned
removed redundant line
added clear write button, renamed variable for consistancy
removed REFLEVEL_ERROR
Merge remote-tracking branch 'mfarhan/clear_trace'
added WSA4000 and WSA50000 v1 error correction
Merge remote-tracking branch 'rwarren/waterfall'