Region API

The following updates should be made to the overall Region API:

• Rename IntervalsSet, PolygonsSet, and PolyhedronsSet to Region1D, Region2D, and Region3D, the reason being that each class can represent the full space, which is decidedly not an interval, polygon, or polyhedron. Also, the term "set", implies that they are collections of objects, which is not the case.
• Create builder APIs for constructing regions in each dimension. Ex:

  Region3D region = Region3D.builder()
      .add(plane1)
      .add(plane2)
      .build();
  

• Absorb RegionFactory functionality into the Region interface or make the utility methods static.