Multi-species spatial version

The program is now spatialised and is working with multiple species. There might still be some errors in the algorithm. What remains to be done:
- Compute the integral of the kernel and add this to Patch::dispersal. This implies the class Dispersal which probably needs to be redone
- Create a Except_Dispersal class which check that the integral of the kernel over Gamma is <= 1 (important for Patch::m_localProducedSeeds)
- Correction of the current bugs/improvements
- Test the program when the kernel is a dirac with an analytical solution