Add particle position vertex information

[Bijan Chokoufe Nejad]

As Mo Xin has observed, Whizard currently does not save the position vertices, as can be seen e.g. in the following .hepevt

 2 211 67 0 170 170 0
  3.2721649710E-02 -7.5987799395E-01 -2.4358109031E+00  2.5556094797E+00  1.3957000000E-01
  0.0000000000E+00  0.0000000000E+00  0.0000000000E+00  0.0000000000E+00  0.0000000000E+00

Full output and sindarin will be attached. The information is in the V PYJETS PYTHIA6 common block. V(1:3) has x,y,z components of the production vertex. V(4) is the production time and V(5) the proper life such that the projected decay vertex will be VP(i=1,2,3) = V(1,2,3) + V(5) * p(1,2,3)/p(0) (in case there is no magnet etc). The particle_t will get V(1,2,3,4) as type(vector4_t), allocatable :: vertex as well as real, allocatable :: lifetime.

It has to be tested that this information is also written to the event formats hepevt, stdhep, lcio, hepmc, ... (please add or remove the relevant formats, I'm not sure)

[Bijan Chokoufe Nejad]

.hepevt cannot be attached as it is too long, c.f. Mo Xin's email or generate yourself.

[Juergen Reuter]

Actually this has been solved meanwhile, as can be seen e.g. in the tauola functional tests etc. Validation by the experimentalists might be pending. This is inpdendent from displaced vertices to be generated by WHIZARD itself for long-lived particles (cf. #427). Closing this one.