Vlasov-Poisson model solver

This simulation of the Vlasov-Poisson system in 1x1v dimensions uses

• NuFI algorithm
• deal.ii FEM package

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Todo:

• Correct dealii solver, check ftilda results to see whats happening
  • implement least squares thingy
  • marry it to fields interpolation
  • make nufi solver use new spline interpolation and evaluation