ENH: Allow -rootSection variable as for VRUI applications

Changed the argument start character for TCLAP commandline
Merge branch 'vrui-rootsection'
Merge branch 'master' into vtk_widgets_support
Added sample configuration files that work for a 3D TV.

Copy the configuration files to the <Vrui-install-dir>/etc directory.
Run the device daemon using
  <Vrui-install-dir>/bin/VRDeviceDaemon -rootSection 3dtv
Run the VruiVTK application using
  VruiVTK -rootSection 3dtv

The configuration files work with an OptiTrack tracker with a VRPN server of
hostname "OptiTrackServer". The Rigid Body Module is used to configure two rigid
bodies, namely, Head and Wand.
DEL: Obsolete TCLAP dependency.

Use Vrui commandline parser instead
Merge branch 'master' into vtk_widgets_support