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
Update test after widget size change.

Change-Id: I6daf54eace03bf2ea80f53fbedb870ed20aeaadb
Merge topic '15100_fix_color_map_editor_size' into next

68a6f38a Update test after widget size change.
c589883e BUG #15100: Increate ColorMapEditor dialog width.