Plotting options

[himoto]

As implemented now, the simulated model time (duration and implicit unit) must be entered in observable.py, however, to truly adapt simulation time, also the plot script needs to be modified. Just as a suggestion, maybe this can be circumvented by adding some time variable to observable.py which is then passed to the plot script? Potentially, this could also include other plotting parameters such as axes limits etc. Some plotting parameters are currently hard coded, maybe there would be a way to dynamically adapt the plot range, potentially circumventing problems when working on several models in parallel.