VOXEDIT: shape improvements

[mgerhardy]

cylinder can only be placed on Y and X planes. trying to place cylinder on Z plane only creates 1vox by the desired length.

shapes other than cylinder don't support placing them on different axes.

code can be found in src/modules/voxelgenerator/ShapeGenerator.h and is called by Modifier::executeShapeAction where currently only the cylinder supports the direction