enable hotstart for moving domain and h-adaptive problems

[cekees]

We need to read the mesh directly from the hdf5 file instead of from the mesh files. In a moving domain or h-adaptive problem the mesh files are only for the first time step.

[adimako]

@tridelat has this been done?

[tridelat]

@adimako it has not, and should not be too much trouble to implement, not a priority on my side but I will look at it when I can