ENH: NucleusEditor allow multiple circle region selection and save the average pixels.
ENH: Allow image turn on/off instead of channels.
ENH: Show up dialog for channel selection for background subtraction in the end;
save background subtracted images in the output folder
ENH: Save the background subtraced image with the same name as tif in the original folder.
Merge branch 'NucleusEditorYan'