1. Add a list of excess population. This unemployed population doesn't produce FIDSI.

2. Allow player to swap FIDSI-producing population with unemployed population.

3. Land ships of migrants into the unemployed population list when the system is full.

4. Let unemployed population diminish over time.

5. Populaion production stops when system is full - as per the default game.

6. Unemployed population have no voting rights nor political representation.


This should allow easier late-game migrations - especially when:

1. most systems are full, 

2. and population generation is very quick (e.g. 1 turn or less), preventing migrating poluations from landing.