fix random cubic anisotropy example (Thanks Raffaele Pellicelli)
open browser on mumax3 w/o arguments
dmi.cu: allow region-dependent parameters
engine: space-dependent DMI (not yet working)
fix dmi order of arguments, all tests pass now
cleanup dmi tests
gui: show maxtorque from last step instead of re-calculation.
Fixes unresponsive gui when torque calc takes longer than refresh