Change the internal representation of alien funds and make 1 evo equal 100 credits.

This doubles class costs and rewards for killing humans. Aliens can collect up to 20 evos (was 9).

Goals:
Cost and value of level[1-4]* aliens are about equal.
Both cost and value can be compared between the teams.
Allows more subtle adjustments of alien class prices.

Human equipment value stays at half its price for now. We should look into this when balancing.