todo

Merge Mike's GUI additions into the main:
	intro has been changed
	main has been changed
	solarsystem has been changed
	SimThread has been added


Needs a planet info window with info on atmosphere and resources
Include added costs for housing in harsh environments



I think the game will crash if one tries to do two transfers of population between the same cities. 
Consider speed advantages to drawing water (and waste) on top of the sphereform instead of the planar form
The distance calculation needs checking. Glasgow to Kisangini (middle of africa) has been observed to be closer than other european cities
expand the implode_and_expand function so that it can be used, on already existing technology. This probably involves adding options for including input_output_dicts in the "common knowledge"
Realitify the variables - find out how large the fossil fuel consumption per capita is, how much energy is produced per fuel. Total energy consumption etc.
Slight speed advantage can be gained by selectively updating the base_position and areas_of_interest dicts selectively when building a new base
AI does not know about mining opportunities at present