Manual scale for color, change approach.

The common interface for color generators extends the MinMaxAdjustable
interface. Manual cand dummy color generators just have blank
implementations.
Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>
Revert "WIP: add a GUI to set the manual color scale."

This reverts commit 93a7863aad9ab73606bbc1d3b9c5f94cb02914c5.
I am unhappy with the design.
Add a getter and a setter methods for the MinMaxAdjustable interface.

Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>
A JDialog to set the min & max properties of a MinMaxAdjustable.

It is now plugged to the spot color generators of the
ConfigureViewsPanel. Nothing more yet.
Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>
Handle the manual color scale nicely on the ColorByFeatureGUIPanel.

The color band now properly displays the manual scale if there is one.
Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>
Integrate fully the manual color scale in the ConfigureViewPanels.

Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>