Overchannel malus added and timer reduced

[Aureus]

We noticed a few cases where there's no real drawback to using overchannel, such as being outnumbered and out of SPs in a door or smobbing in safety. We don't want it to be a completely no-brainer bonus though. So a few tweaks:

• The overchannel status effect now confers -10 db and -10 pb to the channeler for the duration. The added SP and firepower comes at a cost of reduced survivability.
• The status duration has been reduced to 5 minutes to align with the noquit duration. This closes a loophole where a crafty player could gain an advantage by renting to drop the aff, whereas someone abiding by the spirit of the effect was penalized for longer. Penalizing those players didn't feel right.