remove orange frequency toggle buttons
frequency controls in a grid
frequency controls: use QDoubleSpinBox
connect step size dropdown
embiggen QSpinBoxes, arrange 2x2
frequency control: use embedded suffix
remove span calculation from frequency controls
compute span in controller, not frequency controls
no reason to disable labels
disable frequency controls on playback
update changed list in controller if span changed
fix for initial None state
Plot.user_xrange_change signal
user xrange control (Auto mode)
spin box height back to default
make steps selector line up with other widgets
consistency in control group labels
fix fstart/fstop setting bug
two-column device controls
fix some device setting case sensitivity