Limit scheduler memory to prevent system crash

[Philogy]

Especially when running in Dijkstra mode (-d) the scheduler is prone to using increasing amounts of memory until eventually taking over the entire person's computer. In some instances this can cause a system-wide crash if the program isn't exited soon enough.

Suggested Fix

Track the size of the maps in the scheduler and abort at some size. Should be configurable via the CLI and have sane defaults.