calc_resource_changes: Calculate the change in resource, equation 2
In richelbilderbeek/huisweis: Reproduce Huisman And Weissing 1999

Calculate the change in resource, equation 2

1 2	calc_resource_changes(max_growth_rates, resource_densities, hsrs, srcs, species_densities, supply_rates, turnover_rate, mortality_rates)

`max_growth_rates`	max growth rate of all species
`resource_densities`	resource densities
`hsrs`	a matrix of half-saturation constants of species (rows) on resources (columns). Can be created by create_hsrs
`srcs`	a matrix of species' resource content of species (rows) of resources (columns). Can be created by create_srcs
`species_densities`	density of all species
`supply_rates`	the rate at which resources are pumped into the system
`turnover_rate`	the turnover rate of the whole system
`mortality_rates`	mortality rates of all species