Improve/reconcile SwingColorTableWidget and SwingColorBar

[imagejan]

As far as I can see, SwingColorTableWidget currently can be used to display LUTs in input dialogs, but not to actually choose a LUT from a list of available LUTs.

There's also SwingColorBar that seems to serve a similar purpose.

Let's improve the widget to act as a dropdown choice with LUT titles and color bars (with the choices populated from LUTService.findLUTs()), to make it easy to choose color tables in input dialogs.

[NicoKiaru]

I modified the ColorTable widget in order to enable choosing a LUT from it (https://github.com/NicoKiaru/imagej-ui-swing/blob/7e1ae9cdca2180193ee010baa852d24b364f5904/src/main/java/net/imagej/ui/swing/widget/SwingColorTableWidget.java)

However one problem is that it is not well suited for scriptability and recording : there is no trace of the origin of the LUT in the ColorTable object.

I discovered only after this Command https://github.com/imagej/imagej-common/blob/master/src/main/java/net/imagej/lut/LUTSelector.java
This Command uses indeed SwingColorTable Widget for display only, but the advantage is that the lut is only specified by a String from which a ColorTable can be retrieved.