Fix two stupid bugs in MyProbem::set_initial_condition(..)

* I was looping over one too few time values when setting history (need
  to set current value + nprev_values history values).

* I wasn't setting position history! So when the initial condition was x
  dependant the history values were wrong (because x=0 everywhere).
In ODEProblem::set_initial_condition(...) loop over time in normal direction