BiSM_v1 publishable direct rotor-digitization simulation

Main source:
  simF_BiSM_publishable_v1.f90

Compile:
  gfortran -O2 -std=f2008 simF_BiSM_publishable_v1.f90 -o simF_BiSM_publishable_v1.exe

Run:
  ./simF_BiSM_publishable_v1.exe

Outputs:
  BiSM_v1_angle_summary.dat
  BiSM_v1_run_report.txt

Plot:
  gnuplot plot_BiSM_v1.gp

Core calculation:
  Pk = -cos(phiA)cos(phiB)
  Ck = -sin(phiA)sin(phiB)
  Rk = Pk + Ck = -cos(phiA-phiB)

Direct digitization:
  draw u uniformly on [0,1)
  map rsym = 2u-1, uniformly on [-1,+1)
  if rsym < Rk:  DkQ = +1 (equal coincidence)
  otherwise:      DkQ = -1 (not-equal coincidence)

The empirical quaternion correlation is calculated directly from
  (N_eq_data - N_neq_data)/N.

No Malus/Born equal/unequal probability is formed or used in event generation.
A separate local Boolean threshold calculation is retained as the Bell-triangle control.
