Order the variables, only save into memory current status if the user wants to save the runs. Call garbage collector after each run.

When the user does not need to save the runs, then we should not build a complete Habitat Class object which takes a lot of space in memory.

The user can now specify the max number of cores. This helps us to control the ratio of available cores and main memory.

First drafts for the documentation. The inner_procedure is not exported but all other functions are.