emigration cycle resets every time world is loaded, leading to variable behaviour depending on the player's session habits

[master-spike]

Currently, the emigration script is set to run once per month by calling dfhack.timeout(1, 'months', event_loop) at the end of event_loop()

However, timeouted functions are cancelled when the world is unloaded, and when the world is reloaded event_loop() is called again. This means that players who exit and reload often will have a measurably different experience using this script to players who play in long uninterrupted sessions.

The desired behaviour would be for the script to be reload-agnostic, for a consistent gameplay experience.