MB and ZW   Dec 22 2016

This is the code preparing libraries for the SPIN2 example. Alternative 
system of matrix elements for tau pair associated with two jets is provided.
This is quite a big project in itself so we have moved all its elements 
to separate directory SPIN2, where special library is defined.

This example can work as a prototype for such external calculations.
The FORTRAN subroutine which is used for ME calculation is located in ME/SPIN2_distr.f file. 
It need to be called from user program example-VBF.cxx, with the help of F77-C++ interfacing routine.
The implementation  of ME is autonomous from the rest of TAUOLA TauSpinner, except initialization 
routine invoked from the user main program.
  
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To start: =
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 1) open Makefile in SPIN2 directory and follow instruction there.
 2) introduce link to the SPIN2 library into configuration of TAUOLA/TauSpinner/examples/

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HOW TO ACTIVATE SPIN2 in example-VBF.cxx: =
===========================================
1) Modify TAUOLA/TauSpinner/examples/Makefile  uncomment lines containing SPIN2.
2) Modify TAUOLA/TauSpinner/examples/example-VBF/example-VBF.cxx again look for 
   commented lines which contain spin2 or SPIN2.
   Note that example-VBF.cxx will use method  TauSpinner::set_vbfdistrModif(SPIN2::spin2distr);
   and call the F77 spin2distr_() function for calculating ME with the help of C++
   SPIN2::spin2distr method. 
3) You have to export path to SPIN2 library
   export LD_LIBRARY_PATH="/home ... TAUOLA/TauSpinner/examples/example-VBF/SPIN2/lib:$LD_LIBRARY_PATH"
4) Execute Makefile in present SPIN2 directory.
5) You can now compile TAUOLA/TauSpinner/examples/
                       TAUOLA/TauSpinner/examples/example-VBF
   with SPIN2 library activated.
6) If you have your own alternative matrix element you can follow the scheme
   replacing SPIN2 with your own code. SPIN2 can be the understood as an example. 


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Code of SPIN2/MC directory was obtained with the help of Madgraph. Code
was in large part written in F77 with the help of MadGraph, similar as
part of tauspinner library. Naming conflicts with tauspinner library
appeared. In particular for names of subroutines calculating amplitudes.
The names of subroutines calculating amplitudes for ME/SPIN2_functions.f 
had to be changed.

Also distinct versions of Madgraph library functions, 
such as ixxxx  FFV5_3 had to be introduced. These seemed to be  common for 
SPIN2/ME/SPIN2_functions.f and TauSpinner/src/VBF/VBF_functions.f.
This is because different versions of MadGraph were used for
tauspinner library and SPIN2 library construction.

Let us stress, that user code for anomalous amplitudes is expected to be
written in C++ or any other language where features like namespace are
available.
