Preliminary performance rebalancing

Although permanent changes will require detailed testing before implementation, the preliminary testing made the following obvious:

- Big Reactors was just lame performance-wise - this has been corrected
- Atomic Science was way way way too good in the latest build (#160) and has been slashed
- IC2's historic power quadrupling was probably obsolete and has been reverted

I'm swinging low now so we can buff up later. :)