Add methods to Point3D

Added the ability to create a Point3D from another Point3D, to subtract
and divide two Point3Ds, and to compute the distance or square of the
distance between them. Computing the square of the distance is faster
than computing the actual distance.
Make stuff public, fix equals(), add methods
Make triangles protected, fix warning
Merge branch 'master' of ssh://git@github.com/CSUDallas/Geometry2014.git