add_baseband: Add a baseband to a plot.
In brascoball/ggquik: Quick Plotting ggplot2 Wrapper

Add a horizontal or vertical background band (geom_rect) to a plot. This adds the band under most existing layers.

1	add_baseband(gg, direction, min, max, bg_color)

`gg`	The ggplot object on which to add a baseband
`direction`	The direction on which to add the baseband: `x`, or `y`
`min`	The location to start the band
`max`	The location to end the band
`bg_color`	The background color for the band area. Default is `"Green 4"`