Threejstest

getSpecies can slice efficiently in the hdf5 dataset U. Load time and memory usage of say one species at a given timepoint dramatically improved. Internally, the layout of the data i U have changed again. For a given timepoint, the dofs are U[i,:], where 0...Ncells-1 is species A, Ncells...2Ncells-1 speceis B etc. 

Postprocessing routinges may need to change to accomodate for this (unless using getSpecies). 

Now there are two routes to accessing data 
1.) getSpecies - partial IO, never store U in result object. Memory lean. 
2.) U = result["U"], same behavior as before. U added to result object.