Draft: Support restoring the world state by setting the RESTORE_PATH environment variable.

This means that running

> /path/to/experiment arg1 arg2 arg3 ... 42

can be interrupted and that

> RESTORE_PATH=. /path/to/experiment arg1 arg2 arg3 ... 42

will resume it at the last snapshot and continue until the parametrized runtime is reached.

Note that the stochastic parts of the initialization will be repeated, i.e. the seed when restoring must match the seed when saving. This also implies that one cannot change parameters which affect the stochastic parts of the initialization, e.g. the number of flower patches, their flower density or the initial prevalence.