Fixed IC2 conversion ratio and ratio computation

I'm 99.9% sure the IC2 ratio is wrong (it's inverted, relative to the BC ratio). This should be the right one. At least this way one coal gives me the same amount of energy from a BC Stirling Engine and an IC2 Generator (minus the 1% loss in BC). Which seems like a good thing ;-)

Also, the ratio field was always zero, due to the integer division.