Add some new options to control scripts
Add some more field and magnetisation helper construction functions
Add option to modify all (file) output precision and set to 8 decimal places
Improve consistency in interpolation of things for energy derivatives

* Consistently use GeneralInterpolator objects to interpolate magnetostatic field
  Possbily fixes some bugs (if we don't always use an interpolator object
  then the interpolation times will be wrong sometimes).

* Always use BDF2 as time stepper for interpolation when calculating energies
  Using midpoint is dangerous because we can end up with things evaluated
  at the wrong times.

* Add MMInterpolator constructor for alternative time stepper

* Add a self test for midpoint energy (to micromag energies tests)

* Calculate initial energies in semi implict problems as well
Add a proper readme