rework system tests
Since the changes to the local operator (#20 (closed)) cause a number of tests to fail, we can rework the entire set of system tests:
make ODE tests more precise and meaningful
Working on the Dorie 1.0 release resulted in very precise data on L2 error convergence rates for different polynomial orders and grid sizes. This data can be used to make the
ode_higherordertests more precise by demanding the L2 errors measured.
create new reference Miller fields (former #19 (closed))
The Miller field in the reference files has the wrong scaling. The values for K0 range between 10E-5 and 10E-2, which is far to high. Changing the field, however, will break all reference tests.