Added plotting module with command line options.

The file "plot.py" can be used to plot one or more neuroConstruct
simulations previously run. It does not start a simulation itself.
Removed incompatible code for rerunning sims.

Rerunning simulations should now not be needed with the current
implementation anyway.
Fixed and index out of bounds error in analysis.py
Reworked the -p/--parallel option of start_sim.py.

Now the pool size of the process pool can be specified and the options
has been renamed to -p/--pool-size accordingly.
Fixed start_evaluation.py.

This required modifying several modules.
Also the nevo/evaluation.py module has not been fully tested and is
most likely not correct. It should use the nevo/eval/fitness.py module
anyway.
Added plot.py for displaying neurosim.py results.
Chaned pool behaviour and neuroConstruct calls.

The channel values will now be passed via the command line.
Removed dependency on density files completely.

Now the channels of the candidates are send via the command line to
neurosim.py.
Renamed evaluate_param to calc_fitness.

Also evaluate_candidates returns more than just the fitness and should
be used in evaluation.py.
Added output to start_evaluation.py.