Add tests to repository

tests/nb-pair/BrownDyn.bd

tests/nb-pair/analysis/Makefile

tests/nb-pair/analysis/boltzmann-check.plt.py

tests/nb-pair/analysis/get-data.tcl

tests/nb-pair/analysis/plotTools.py

tests/nb-pair/analysis/test.tcl

tests/nb-pair/diffusion.POT.dx

tests/nb-pair/dummy-pot.dat

tests/nb-pair/dummy-pot.py

tests/nb-pair/extend114_pot-pot.dat

tests/nb-pair/null-pot.dat

tests/nb-pair/null.dx

tests/nb-pair/null2.dx

tests/nb-pair/run.sh