VOXEDIT: if you update the alpha channel value of the current selected voxel in the palette, the cursor voxel is not updated

[mgerhardy]

the cursor voxel needs updating of its flags, too

the screenshots should existing voxels (index 0) that were placed in the scene, then index 0 in the palette widget got a little transparency. If you now place new voxels with index 0, they don't end up transparent