"Vacuum" labelled volumes from GDML have "Vacuum" sensitivity

[Laurie Nevay]

Make sure that the volumes categorised as namedVacuumVolumes in GDML loaded as a generic element have the vacuum sensitivity attached the same as the rest of BDSIM instead of the default energy deposition one. Will eliminate extremely low ionisation energy losses in imported geometry.

[Laurie Nevay]

Added for the next version. Also, added an option:

option, verboseSensitivity=1;

to see the name of the sensitive detector attached to every single volume.