Lima/vecgeom 206 v2 - Fixes bugs in tube's kernels
This branch fixes bugs on the tube kernels:
- fixes to calculations of DistanceToIn() and DistanceToOut() for points on the surface of phi-wedges.
- resets returned distances to zero when within Tolerance from zero (near a surface).
- avoid all negative values from SafetyToOut(), returning zero instead. Note that DistanceToIn() can return negative values, since no Geant4 complaints have been observed so far.
See [JIRA issue VecGeom-206|https://its.cern.ch/jira/browse/VECGEOM-206] for a more complete description. See also comments on closed [Merge request #51|!51 (closed)].