lima/vecgeom 226 - Shape tester fixes for the trapezoid
This branch fixes all ShapeTester problems in both configurations of the trapezoid (VECGEOM_PLANESHELL_DISABLE=ON or OFF).
It also fixes a bug in the vectorized DistanceToIn(), identified after the first round of trapezoid fixes (PLANESHELL=ON).
All unit tests passing (using gcc 4.9.3) for -DUSOLIDS=ON -DROOT=ON -DGEANT4=ON -DBENCHMARK=ON -DCTEST=ON and -DBACKEND=Vc.