Event Generator Status Report

1) Working examples for Pythia6, Pythia8 and (limited) Pepsi event generators with
    a (simple) event header and particle record.  Hijing is next on the TODO list.

2) Particles are saved in a StarGenParticle class which

    (a) Provides the /HEPEVT/ information
    (b) Adds additional information specifying
        - which generator it originated from
        - the index in the event generator's event record
        - the index in the master event record
        - the index in the geant (g2t particle) record
    (c) all particles are saved in the StarGenEvent record, unlike current framework in
         which only particles which are pushed out to geant are saved
    (d) added a TRefArray to StarGenEvent so that user can access the generated
         particle if they have the (so called) “primary key” from the St_particle table.

3) StarGenPPEvent and StarGenEPEvent records implemented.  Next will be
    StarGenAAEvent and StarGenEAEvent

4) Have capability to write a TTree and (partial) read back events from a TTree.  Have
    generated Pythia8 W--> e nu sample with Pythia6 minbias backrgound as a test...