Minor changes in workshop 1 to bring in feed back from people.
Fix problem with displaying external figures.
Clear workshop 1 from the scatter function.
Other minor adjustments.
Complete save plot section.
Modify exercise 2 to include harmonic oscillator.
Replace png figures in exercises by svg.
Some adjustments on exercise 2 and rewriting of exercise 3.
Merge branch 'master' of ch-general1.ch.ic.ac.uk:/home/jbettenc/teaching/python_workshops
Hacking on workshop 2`
Removed output