Reseting rocktype color grouping caused the scene to show rock color unexpectedly

[Angus Yeh]

Changing the colorbar object should not trigger the display of the variable in scene.

[Angus Yeh]

Fix Issue #41 of scene shows rock color unexpectedly while reseting rocktype color grouping while current color is other variable.

This is done so the scene.clearCache() will automatically refresh color if that's the currently shown. It replaces the additional routine of refresh current color.

→ <<cset fb0d09c97593>>