Setting up test problem object
Removed class.

Use functions to make wrapping with python easier
2D test problems.

I copied most of this code from local/fftw.
It makes a good base for building the test setups.
1D problem setup
3D test problem setup.

Also fixed error in 3d solver. I was not adding kz to k2.
This made the exact solution be inv prop to 2*k2, not 3*k2.