Apply auto-symmetrisation of vetoes to the fully symmetric case. Also implement the more efficient scheme for calculating the amplitude in the fully symmetric case - roughly halves time to generate toy experiments in GenFit3KS example.

git-svn-id: svn+ssh://phab.hepforge.org/source/laurasvn/trunk@434 30227d83-a2f9-49e9-9e98-657c83b2c86a