Made the gain correction system like the walk correction system

Specify a gain correction:

Event->setGainCorrection(Correction,channel);

Setting a correction beyond the range of the current corrections will fill in the corrections with
defualt 1.

root [3] e->setGainCorrections(124,0)
root [4] e->setGainCorrections(12,8)
root [5] e->dumpGainCorrections()
***Dump gain Corrections***
gain correction for channel 0 124
gain correction for channel 1 1
gain correction for channel 2 1
gain correction for channel 3 1
gain correction for channel 4 1
gain correction for channel 5 1
gain correction for channel 6 1
gain correction for channel 7 1
gain correction for channel 8 12