Potential and Kinetic Energies are calculated seperately
(in the c Part of the program)
Temperature and Pressure are measured in ljsim.py
and plotted in ljanalyze.py.

There is a problem with the plots: when the simulation was done
in several steps (i.e. continued), the plots start again
at t=0
Solved problem with plotting

The time always started at 0 when the simulation was continued.
Now it is set to the time of the last timestep (from ljsim.dat)
Merge branch 'andi'