Extended functionality related to volume calculation

• m_volume added into GeoShape

• volume(int npoints)

User can now specify the number of random points to be used for estimation the volume, the default is 1M points

• getVolumeValue(), setVolumeValue()

First method just returns current value of m_volume, second method sets m_volume

• isPolyhedron()

Returns true if all constituents of the shape are polyhedra, false otherwise

• getNoConstituents()

Returns total number of constituents

• Volume of GeoShapeUnion(A,B) is now calculated as:

A.volume() + B.volume() - GeoShapeIntersection(A,B).volume()

• Volume of GeoShapeSubtraction(A,B) is now calculated as:

A.volume() - GeoShapeIntersection(A,B).volume()