Wave Fd python convergence limits Explicit Fourier/Spline

[eusoubrasileiro]

• Look after solution to find why there is so much exponential growth.
  Source might not be a reason due that fact that implicit is working perfectly.
  Should after last trials post on stackoverflow.

[eusoubrasileiro]

Theory is totally difference due the fact its no finite differences to calculate derivatives. Fourier borders might need especial care. The source is not the problem certainly.

[eusoubrasileiro]

We will not try on Fourier for now (abandon). We will use finite differences.