BUG #15100: Increate ColorMapEditor dialog width.

Making default width for the ColorMapEditor dock panel to be large
enough to not need horizontal scroll bars.

Also updating all dock panels that we expect to be docked vertically to
not allow docking on the horizontal dockable regions -- improving
usability.

Change-Id: I0fd17d08e566c471cd87f0f575f3c787f91a6efb
Merge topic '15100_fix_color_map_editor_size' into next

3ab86159 BUG #15100: Increate ColorMapEditor dialog width.