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

Spatial version without reproduction

The program is now spatially explicit, but some work remains to be done:

• Reproduction:
  • Forest must find neighbours of each patch
  • For each patch, either there is already a pop or not (if not, create a new one)
• Environment:
  • Env must know which pop owns it

Non-fully spatial

Contains the main files for spatial version. The objects are spatialised, but neither the dynamics (advection equation), nor reproduction are ready.

To do:

1. Add double localSeedsProduced and double localSeedBank to population.h++
2. Add kernel (Maybe create a new object to describe reachable cells from a source for each species, and each cell of the lattice)
3. Transfer the localSeedBank to new cohort