Quadtree and other sampling methods

[falkamelung]

We should think about sampling code for mimtpy, as this is always a headache. Let's list here the different sampling code. We need the ability to switch between sampling methods and assess whether sampling has any effect on the solution. Lets list here the different sampling codes that we could try:

• Kite from Pyrocko
• Bill Barnhart:
  https://myweb.uiowa.edu/wbarnhart/software.html
• Sjonni Jonsson's group (hist student Rishabh Dutta is on GitHub), I should ask.
• Wenliang Zhao
  https://github.com/wzds2015/RemoteSensing_Geophysics/blob/master/glacier/quadtree