Add histogram to napariGater

[emir-radkevich]

Added histogram of values that should be gated as a separate widget in napariGater.py

[ajitjohnson]

this is great, thank you. could you please move the qt related imports into

try:
    import napari
    from magicgui import magicgui
except ImportError:
    pass

we do this so that people can install scimap without GUI related activities. thank you.

[emir-radkevich]

this is great, thank you. could you please move the qt related imports into

try:
    import napari
    from magicgui import magicgui
except ImportError:
    pass

we do this so that people can install scimap without GUI related activities. thank you.

done.

[ajitjohnson]

thank you incorporated into 2.3.3 - added some cosmetic upgrades.