Adding CheckBox to set output volume as label map
move output box and labelmap checkbox to self variables
Update node selector and checkbox with LabelMap state
ENH: When a labelmap input is selected the output changes to labelmap
ENH: print object oriented python code to create filter before running
STYLE: move apply bottom to match CLI interface
ENH: improving responsiveness of main_queue_process

Exiting from python does not release the GIL, it's better to empty the
QT event queue and then sleep to maintain responsiveness and
alternating between the thread needing python code. Additionally,
better error message handle was added.