Make PISA examples self-contained

[asogaard]

Is your feature request related to a problem? Please describe.
With #378 most examples scripts are self-contained, i.e. referring only to files that come bundled with the repo. The only exception is the PISA ones.

Describe the solution you'd like
It would be nice if all the example scripts we provide, including the PISA ones, could be run out of the box, provided of course that the necessary packages are installed. This is also requested here: openjournals/joss-reviews#4971 (comment).

Describe alternatives you've considered
If we want to keep our examples self-contained, the alternative would be to not provide examples on the interface with PISA, but I think this would be a shame.

[RasmusOrsoe]

@asogaard as discussed with you and @philippeller , we cannot do this unless we have significantly higher statistics in our public data. (Running a minimizer on ~5 events wont work). So I think we can close this.

[asogaard]

Closing in favour of #428