Adding in normalizer functionality, listeners in FRB

[munkm]

Listeners have been added in the colormaps widget for changes in

• colormap name
• whether the scale is log
• min
• max
• the data array these trigger a renormalize() when changed.

In the FRB a listeners for the image_array is set up. If this is triggered a redraw function is called.

Logic has been modified in the add_cmaps() function to check whether a wasm colormaps object has been made/created.

[munkm]

Other notes:

• Right now i've left the widget name to colormaps. If it's more accurate/clear to rename it normalizer I can push a fix for that.
• I also need to push a modification so normalize() only uses the model object variables, and not arbitrary variables that you send it. Min and max area already set this way, but map name, data, and log scale are not.