stopTracks confusing and doesn't work as intended

[Laurie Nevay]

The function of stopTracks is unclear. From inspecting the code it appears to be intended to kill secondary electrons, gammas, positrons, protons and antiprotons only. This is just a more specific version of stopSecondaries. From the description the functionality should be to stop particles at their first interaction.

The name stopTracks is ambiguous as a 'track' in Geant4 terminology is a snapshot of any particle between a pre and post step point.

[Laurie Nevay]

This has been removed in develop (from v0.994). There is now only stopSecondaries. New tracking cuts 'minimumRangeandminimumKineticEnergy` were added to provided speed up in simulation when used with caution.