Merge pull request #20 from jp90/master

jp auf aktuellen stand
even more stencils
derivatives added
little stencil error corrected
ableitungen ohne alpha
even more corrections stencil
Merge pull request #22 from jp90/JP

Jp
main outer loop
computations momentum
velocity updates, Py added, alpha teilweise in ableitungen entfernt
schrittweiten dx und dy in inputvals eingefügt, computetimesteps geschrieben
include SimIO in solver class, residuum calculation
return res
residuum corrected
Merge pull request #23 from jp90/master

Merge pull request #22 from jp90/JP
Merge pull request #25 from jp90/master

update