Migration when above F_Th

[simoncarrignon]

When the population is above F_Th, so far the migrants group will move after multiple time step. It should not happend with real scenario, but happen when initial population have big population size wrt F_Th. While loop should be introduce in order to have multiple 'waves' of migrants that move until $Ni < F{Th}$ where $N_i$ is the population of the community $i$

[simoncarrignon]

Another problem: When birth rate is high and we have big family close to $F_{Th}$, it often happens that no migration happens. This in turn generates cases where new communities are created through fissionComunity that ends up empty.